Drosophila melanogaster

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Drosophila melanogaster_table_infobox_0

Drosophila melanogasterDrosophila melanogaster_header_cell_0_0_0
Scientific classificationDrosophila melanogaster_header_cell_0_1_0
Kingdom:Drosophila melanogaster_cell_0_2_0 AnimaliaDrosophila melanogaster_cell_0_2_1
Phylum:Drosophila melanogaster_cell_0_3_0 ArthropodaDrosophila melanogaster_cell_0_3_1
Class:Drosophila melanogaster_cell_0_4_0 InsectaDrosophila melanogaster_cell_0_4_1
Order:Drosophila melanogaster_cell_0_5_0 DipteraDrosophila melanogaster_cell_0_5_1
Family:Drosophila melanogaster_cell_0_6_0 DrosophilidaeDrosophila melanogaster_cell_0_6_1
Genus:Drosophila melanogaster_cell_0_7_0 DrosophilaDrosophila melanogaster_cell_0_7_1
Subgenus:Drosophila melanogaster_cell_0_8_0 SophophoraDrosophila melanogaster_cell_0_8_1
Species group:Drosophila melanogaster_cell_0_9_0 Drosophila melanogaster groupDrosophila melanogaster_cell_0_9_1
Species subgroup:Drosophila melanogaster_cell_0_10_0 Drosophila melanogaster subgroupDrosophila melanogaster_cell_0_10_1
Species complex:Drosophila melanogaster_cell_0_11_0 Drosophila melanogaster complexDrosophila melanogaster_cell_0_11_1
Species:Drosophila melanogaster_cell_0_12_0 D. melanogasterDrosophila melanogaster_cell_0_12_1
Binomial nameDrosophila melanogaster_header_cell_0_13_0

Drosophila melanogaster is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. Drosophila melanogaster_sentence_0

The species is known generally as the common fruit fly or vinegar fly. Drosophila melanogaster_sentence_1

Starting with Charles W. Woodworth's proposal of the use of this species as a model organism, D. melanogaster continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and life history evolution. Drosophila melanogaster_sentence_2

As of 2017, six Nobel prizes had been awarded for research using Drosophila. Drosophila melanogaster_sentence_3

D. melanogaster is typically used in research owing to its rapid life cycle, relatively simple genetics with only four pairs of chromosomes, and large number of offspring per generation. Drosophila melanogaster_sentence_4

It was originally an African species, with all non-African lineages having a common origin. Drosophila melanogaster_sentence_5

Its geographic range includes all continents, including islands. Drosophila melanogaster_sentence_6

D. melanogaster is a common pest in homes, restaurants, and other places where food is served. Drosophila melanogaster_sentence_7

Flies belonging to the family Tephritidae are also called "fruit flies". Drosophila melanogaster_sentence_8

This can cause confusion, especially in the Mediterranean, Australia, and South Africa, where the Mediterranean fruit fly Ceratitis capitata is an economic pest. Drosophila melanogaster_sentence_9

Physical appearance Drosophila melanogaster_section_0

Wild type fruit flies are yellow-brown, with brick-red eyes and transverse black rings across the abdomen. Drosophila melanogaster_sentence_10

The brick-red color of the eyes of the wild type fly are due to two pigments. Drosophila melanogaster_sentence_11

Xanthommatin, which is brown and is derived from tryptophan, and drosopterins, which are red and are derived from guanosine triphosphate. Drosophila melanogaster_sentence_12

They exhibit sexual dimorphism; females are about 2.5 mm (0.10 in) long; males are slightly smaller with darker backs. Drosophila melanogaster_sentence_13

Males are easily distinguished from females based on colour differences, with a distinct black patch at the abdomen, less noticeable in recently emerged flies, and the sexcombs (a row of dark bristles on the tarsus of the first leg). Drosophila melanogaster_sentence_14

Furthermore, males have a cluster of spiky hairs (claspers) surrounding the reproducing parts used to attach to the female during mating. Drosophila melanogaster_sentence_15

Extensive images are found at FlyBase. Drosophila melanogaster_sentence_16

Lifecycle and reproduction Drosophila melanogaster_section_1

Under optimal growth conditions at 25 °C (77 °F), the D. melanogaster lifespan is about 50 days from egg to death. Drosophila melanogaster_sentence_17

The developmental period for D. melanogaster varies with temperature, as with many ectothermic species. Drosophila melanogaster_sentence_18

The shortest development time (egg to adult), 7 days, is achieved at 28 °C (82 °F). Drosophila melanogaster_sentence_19

Development times increase at higher temperatures (11 days at 30 °C or 86 °F) due to heat stress. Drosophila melanogaster_sentence_20

Under ideal conditions, the development time at 25 °C (77 °F) is 8.5 days, at 18 °C (64 °F) it takes 19 days and at 12 °C (54 °F) it takes over 50 days. Drosophila melanogaster_sentence_21

Under crowded conditions, development time increases, while the emerging flies are smaller. Drosophila melanogaster_sentence_22

Females lay some 400 eggs (embryos), about five at a time, into rotting fruit or other suitable material such as decaying mushrooms and sap fluxes. Drosophila melanogaster_sentence_23

Drosophila melanogaster is a holometabolous insect, so it undergoes a full metamorphosis. Drosophila melanogaster_sentence_24

Their life cycle is broken down into 4 stages: embryo, larva, pupa, adult. Drosophila melanogaster_sentence_25

The eggs, which are about 0.5 mm long, hatch after 12–15 hours (at 25 °C or 77 °F). Drosophila melanogaster_sentence_26

The resulting larvae grow for about 4 days (at 25 °C) while molting twice (into second- and third-instar larvae), at about 24 and 48 h after hatching. Drosophila melanogaster_sentence_27

During this time, they feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit itself. Drosophila melanogaster_sentence_28

The mother puts feces on the egg sacs to establish the same microbial composition in the larvae's guts that has worked positively for herself. Drosophila melanogaster_sentence_29

Then the larvae encapsulate in the puparium and undergo a 4-day-long metamorphosis (at 25 °C), after which the adults eclose (emerge). Drosophila melanogaster_sentence_30

Males perform a sequence of five behavioral patterns to court females. Drosophila melanogaster_sentence_31

First, males orient themselves while playing a courtship song by horizontally extending and vibrating their wings. Drosophila melanogaster_sentence_32

Soon after, the male positions himself at the rear of the female's abdomen in a low posture to tap and lick the female genitalia. Drosophila melanogaster_sentence_33

Finally, the male curls his abdomen and attempts copulation. Drosophila melanogaster_sentence_34

Females can reject males by moving away, kicking, and extruding their ovipositor. Drosophila melanogaster_sentence_35

Copulation lasts around 15–20 minutes, during which males transfer a few hundred, very long (1.76 mm) sperm cells in seminal fluid to the female. Drosophila melanogaster_sentence_36

Females store the sperm in a tubular receptacle and in two mushroom-shaped spermathecae; sperm from multiple matings compete for fertilization. Drosophila melanogaster_sentence_37

A last male precedence is believed to exist; the last male to mate with a female sires about 80% of her offspring. Drosophila melanogaster_sentence_38

This precedence was found to occur through both displacement and incapacitation. Drosophila melanogaster_sentence_39

The displacement is attributed to sperm handling by the female fly as multiple matings are conducted and is most significant during the first 1–2 days after copulation. Drosophila melanogaster_sentence_40

Displacement from the seminal receptacle is more significant than displacement from the spermathecae. Drosophila melanogaster_sentence_41

Incapacitation of first male sperm by second male sperm becomes significant 2–7 days after copulation. Drosophila melanogaster_sentence_42

The seminal fluid of the second male is believed to be responsible for this incapacitation mechanism (without removal of first male sperm) which takes effect before fertilization occurs. Drosophila melanogaster_sentence_43

The delay in effectiveness of the incapacitation mechanism is believed to be a protective mechanism that prevents a male fly from incapacitating his own sperm should he mate with the same female fly repetitively. Drosophila melanogaster_sentence_44

Sensory neurons in the uterus of female D. melanogaster respond to a male protein, sex peptide, which is found in semen. Drosophila melanogaster_sentence_45

This protein makes the female reluctant to copulate for about 10 days after insemination. Drosophila melanogaster_sentence_46

The signal pathway leading to this change in behavior has been determined. Drosophila melanogaster_sentence_47

The signal is sent to a brain region that is a homolog of the hypothalamus and the hypothalamus then controls sexual behavior and desire. Drosophila melanogaster_sentence_48

Gonadotropic hormones in Drosophila maintain homeostasis and govern reproductive output via a cyclic interrelationship, not unlike the mammalian estrous cycle. Drosophila melanogaster_sentence_49

Sex peptide perturbs this homeostasis and dramatically shifts the endocrine state of the female by inciting juvenile hormone synthesis in the corpus allatum. Drosophila melanogaster_sentence_50

D. melanogaster is often used for life extension studies, such as to identify genes purported to increase lifespan when mutated. Drosophila melanogaster_sentence_51

D. melanogaster is also used in studies of aging. Drosophila melanogaster_sentence_52

Werner syndrome is a condition in humans characterized by accelerated aging. Drosophila melanogaster_sentence_53

It is caused by mutations in the gene WRN that encodes a protein with essential roles in repair of DNA damage. Drosophila melanogaster_sentence_54

Mutations in the D. melanogaster homolog of WRN also cause increased physiologic signs of aging, such as shorter lifespan, higher tumor incidence, muscle degeneration, reduced climbing ability, altered behavior and reduced locomotor activity. Drosophila melanogaster_sentence_55

Females Drosophila melanogaster_section_2

Females become receptive to courting males about 8–12 hours after emergence. Drosophila melanogaster_sentence_56

Specific neuron groups in females have been found to affect copulation behavior and mate choice. Drosophila melanogaster_sentence_57

One such group in the abdominal nerve cord allows the female fly to pause her body movements to copulate. Drosophila melanogaster_sentence_58

Activation of these neurons induces the female to cease movement and orient herself towards the male to allow for mounting. Drosophila melanogaster_sentence_59

If the group is inactivated, the female remains in motion and does not copulate. Drosophila melanogaster_sentence_60

Various chemical signals such as male pheromones often are able to activate the group. Drosophila melanogaster_sentence_61

Also, females exhibit mate choice copying. Drosophila melanogaster_sentence_62

When virgin females are shown other females copulating with a certain type of male, they tend to copulate more with this type of male afterwards than naive females (which have not observed the copulation of others). Drosophila melanogaster_sentence_63

This behavior is sensitive to environmental conditions, and females copulate less in bad weather conditions. Drosophila melanogaster_sentence_64

Males Drosophila melanogaster_section_3

Polygamy Drosophila melanogaster_section_4

Both male and female D. melanogaster flies act polygamously (having multiple sexual partners at the same time). Drosophila melanogaster_sentence_65

In both males and females, polygamy results in a decrease in evening activity compared to virgin flies, more so in males than females. Drosophila melanogaster_sentence_66

Evening activity consists of those in which the flies participate other than mating and finding partners, such as finding food. Drosophila melanogaster_sentence_67

The reproductive success of males and females varies, because a female only needs to mate once to reach maximum fertility. Drosophila melanogaster_sentence_68

Mating with multiple partners provides no advantage over mating with one partner, so females exhibit no difference in evening activity between polygamous and monogamous individuals. Drosophila melanogaster_sentence_69

For males, however, mating with multiple partners increases their reproductive success by increasing the genetic diversity of their offspring. Drosophila melanogaster_sentence_70

This benefit of genetic diversity is an evolutionary advantage because it increases the chance that some of the offspring will have traits that increase their fitness in their environment. Drosophila melanogaster_sentence_71

The difference in evening activity between polygamous and monogamous male flies can be explained with courtship. Drosophila melanogaster_sentence_72

For polygamous flies, their reproductive success increases by having offspring with multiple partners, and therefore they spend more time and energy on courting multiple females. Drosophila melanogaster_sentence_73

On the other hand, monogamous flies only court one female, and expend less energy doing so. Drosophila melanogaster_sentence_74

While it requires more energy for male flies to court multiple females, the overall reproductive benefits it produces has kept polygamy as the preferred sexual choice. Drosophila melanogaster_sentence_75

The mechanism that affects courtship behavior in Drosophila is controlled by the oscillator neurons DN1s and LNDs. Drosophila melanogaster_sentence_76

Oscillation of the DN1 neurons was found to be effected by sociosexual interactions, and is connected to mating-related decrease of evening activity. Drosophila melanogaster_sentence_77

Model organism in genetics Drosophila melanogaster_section_5

D. melanogaster remains one of the most studied organisms in biological research, particularly in genetics and developmental biology. Drosophila melanogaster_sentence_78

D. melanogaster also has impact in environmental studies and mutagenesis. Drosophila melanogaster_sentence_79

History of use in genetic analysis Drosophila melanogaster_section_6

D. melanogaster was among the first organisms used for genetic analysis, and today it is one of the most widely used and genetically best-known of all eukaryotic organisms. Drosophila melanogaster_sentence_80

All organisms use common genetic systems; therefore, comprehending processes such as transcription and replication in fruit flies helps in understanding these processes in other eukaryotes, including humans. Drosophila melanogaster_sentence_81

Thomas Hunt Morgan began using fruit flies in experimental studies of heredity at Columbia University in 1910 in a laboratory known as the Fly Room. Drosophila melanogaster_sentence_82

The Fly Room was cramped with eight desks, each occupied by students and their experiments. Drosophila melanogaster_sentence_83

They started off experiments using milk bottles to rear the fruit flies and handheld lenses for observing their traits. Drosophila melanogaster_sentence_84

The lenses were later replaced by microscopes, which enhanced their observations. Drosophila melanogaster_sentence_85

Morgan and his students eventually elucidated many basic principles of heredity, including sex-linked inheritance, epistasis, multiple alleles, and gene mapping. Drosophila melanogaster_sentence_86

D. melanogaster had historically been used in laboratories to study genetics and patterns of inheritance. Drosophila melanogaster_sentence_87

However, D. melanogaster also has importance in environmental research and mutagenesis. Drosophila melanogaster_sentence_88

Being such great model organisms allows researchers to introduce mutagens and observe the impact. Drosophila melanogaster_sentence_89

Reasons for use in laboratories Drosophila melanogaster_section_7

There are many reasons the fruit fly is a popular choice as a model organism: Drosophila melanogaster_sentence_90

Drosophila melanogaster_unordered_list_0

  • Its care and culture require little equipment, space, and expense even when using large cultures.Drosophila melanogaster_item_0_0
  • It can be safely and readily anesthetized (usually with ether, carbon dioxide gas, by cooling, or with products such as FlyNap).Drosophila melanogaster_item_0_1
  • Its morphology is easy to identify once anesthetized.Drosophila melanogaster_item_0_2
  • It has a short generation time (about 10 days at room temperature), so several generations can be studied within a few weeks.Drosophila melanogaster_item_0_3
  • It has a high fecundity (females lay up to 100 eggs per day, and perhaps 2000 in a lifetime).Drosophila melanogaster_item_0_4
  • Males and females are readily distinguished, and virgin females are easily isolated, facilitating genetic crossing.Drosophila melanogaster_item_0_5
  • The mature larva has giant chromosomes in the salivary glands called polytene chromosomes, "puffs", which indicate regions of transcription, hence gene activity. The under-replication of rDNA occurs resulting in only 20% of DNA compared to the brain. Compare to the 47%, less rDNA in Sarcophaga barbata ovaries.Drosophila melanogaster_item_0_6
  • It has only four pairs of chromosomes – three autosomes, and one pair of sex chromosomes.Drosophila melanogaster_item_0_7
  • Males do not show meiotic recombination, facilitating genetic studies.Drosophila melanogaster_item_0_8
  • Recessive lethal "balancer chromosomes" carrying visible genetic markers can be used to keep stocks of lethal alleles in a heterozygous state without recombination due to multiple inversions in the balancer.Drosophila melanogaster_item_0_9
  • The development of this organism—from fertilized egg to mature adult—is well understood.Drosophila melanogaster_item_0_10
  • Genetic transformation techniques have been available since 1987.Drosophila melanogaster_item_0_11
  • Its complete genome was sequenced and first published in 2000.Drosophila melanogaster_item_0_12
  • Sexual mosaics can be readily produced, providing an additional tool for studying the development and behavior of these flies.Drosophila melanogaster_item_0_13

Genetic markers Drosophila melanogaster_section_8

See also: Abdominal pigmentation in Drosophila melanogaster Drosophila melanogaster_sentence_91

Genetic markers are commonly used in Drosophila research, for example within balancer chromosomes or P-element inserts, and most phenotypes are easily identifiable either with the naked eye or under a microscope. Drosophila melanogaster_sentence_92

In the list of a few common markers below, the allele symbol is followed by the name of the gene affected and a description of its phenotype. Drosophila melanogaster_sentence_93

(Note: Recessive alleles are in lower case, while dominant alleles are capitalised.) Drosophila melanogaster_sentence_94

Drosophila melanogaster_unordered_list_1

  • Cy: Curly; the wings curve away from the body, flight may be somewhat impairedDrosophila melanogaster_item_1_14
  • e: Ebony; black body and wings (heterozygotes are also visibly darker than wild type)Drosophila melanogaster_item_1_15
  • Sb: Stubble; bristles are shorter and thicker than wild typeDrosophila melanogaster_item_1_16
  • w: White; eyes lack pigmentation and appear whiteDrosophila melanogaster_item_1_17
  • bw: Brown; eye color determined by various pigments combined.Drosophila melanogaster_item_1_18
  • y: Yellow; body pigmentation and wings appear yellow, the fly analog of albinismDrosophila melanogaster_item_1_19

Classic genetic mutations Drosophila melanogaster_section_9

Drosophila genes are traditionally named after the phenotype they cause when mutated. Drosophila melanogaster_sentence_95

For example, the absence of a particular gene in Drosophila will result in a mutant embryo that does not develop a heart. Drosophila melanogaster_sentence_96

Scientists have thus called this gene tinman, named after the Oz character of the same name. Drosophila melanogaster_sentence_97

Likewise changes in the Shavenbaby gene cause the loss of dorsal cuticular hairs in Drosophila sechellia larvae. Drosophila melanogaster_sentence_98

This system of nomenclature results in a wider range of gene names than in other organisms. Drosophila melanogaster_sentence_99

Drosophila melanogaster_unordered_list_2

  • Adh: Alcohol dehydrogenase- Drosophila melanogaster can express the alcohol dehydrogenase (ADH) mutation, thereby preventing the breakdown of toxic levels of alcohols into aldehydes and ketones. While ethanol produced by decaying fruit is a natural food source and location for oviposit for Drosophila at low concentrations (<4%), high concentrations of ethanol can induce oxidative stress and alcohol intoxication. Drosophila’s fitness is elevated by consuming the low concentration of ethanol. Initial exposure to ethanol causes hyperactivity, followed by incoordination and sedation. Further research has shown that the antioxidant alpha-ketoglutarate may be beneficial in reducing the oxidative stress produced by alcohol consumption. A 2016 study concluded that food supplementation with 10-mM alpha-ketoglutarate decreased Drosophila alcohol sensitivity over time. For the gene that codes for ADH, there are 194 known classic and insertion alleles. Two alleles that are commonly used for experimentation involving ethanol toxicity and response are ADH (slow) and ADH (fast). Numerous experiments have concluded that the two alleles account for the differences in enzymatic activity for each. In comparing Adh-F homozygotes (wild-type) and Adh- nulls (homozygous null), research has shown that Adh- nulls have a lower level of tolerance for ethanol, starting the process of intoxication earlier than its counter partner. Other experiments have also concluded that the Adh allele is haplosufficient. Haplosuffiency states that having one functioning allele will be adequate in producing the needed phenotypes for survival. Meaning that flies that were heterozygous for the Adh allele (one copy of the Adh null allele and one copy of the Adh Wild type allele) gave very similar phenotypical alcohol tolerance as the homozygous dominant flies (two copies of the wild type Adh allele). Regardless of genotype, Drosophila show a negative response to exposure to samples with an ethanol content above 5%, which render any tolerance inadequate, resulting in a lethal dosage and a mortality rate of around 70%. Drosophila show many of the same ethanol responses as humans do. Low doses of ethanol produce hyperactivity, moderate doses incoordination, and high doses sedation.”.Drosophila melanogaster_item_2_20
  • b: black- The black mutation was discovered in 1910 by Thomas Hunt Morgan. The black mutation results in a darker colored body, wings, veins, and segments of the fruit fly's leg. This occurs due to the fly's inability to create beta-alanine, a beta amino acid. The phenotypic expression of this mutation varies based on the genotype of the individual; for example, whether the specimen is homozygotic or heterozygotic results in a darker or less dark appearance. This genetic mutation is x-linked recessive.Drosophila melanogaster_item_2_21
  • bw: brown- The brown eye mutation results from pteridine (red) pigments inability to be produced or synthesized, due to a point mutation on chromosome II. When the mutation is homozygous, the pteridine pigments are unable to be synthesized because in the beginning of the pteridine pathway, a defective enzyme is being coded by homozygous recessive genes. In all, mutations in the pteridine pathway produces a darker eye color, hence the resulting color of the biochemical defect in the pteridine pathway being brown.Drosophila melanogaster_item_2_22
  • m: miniature- One of the first records of the miniature mutation of wings was also made by Thomas Hunt Morgan in 1911. He described the wings as having a similar shape as the wild-type phenotype. However, their miniature designation refers to the lengths of their wings, which do not stretch beyond their body and, thus, are notably shorter than the wild-type length. He also noted its inheritance is connected to the sex of the fly and could be paired with the inheritance of other sex-determined traits such as white eyes. The wings may also demonstrate other characteristics deviant from the wild-type wing, such as a duller and cloudier color. Miniature wings are 1.5x shorter than wild-type but are believed to have the same number of cells. This is due to the lack of complete flattening by these cells, making the overall structure of the wing seem shorter in comparison. The pathway of wing expansion is regulated by a signal-receptor pathway, where the neurohormone bursicon interacts with its complementary G protein-coupled receptor; this receptor drives one of the G-protein subunits to signal further enzyme activity and results in development in the wing, such as apoptosis and growth.Drosophila melanogaster_item_2_23
  • se: sepia- The sepia eye color is brown. Ommochromes[brown] and drosopterins[red] are responsible for the typical eye color of Drosophila melanogaster. These mutations occur on the third chromosome. It is due to the inability of the sepia to manufacture a pteridine enzyme that is responsible for the red pigmentation, that they are unable to display the red coloration of the eyes, and instead have the brown coloration as mentioned earlier. When mated with a wild type, flies with red eyes will be dominant over sepia color eyes. They are then classified as a recessive mutation, and can only result when both chromosomes contain the gene for sepia eyes. Sepia colored eyes are not dependent on the sex of the fly. The Sepia eye color decreases sexual activity in males and influences preference of females.”Drosophila melanogaster_item_2_24
  • v: vermilion- Vermilion eye color compared to a wild type D. melanogaster is a radiant red. Vermilion eye color mutant is sex-linked recessive gene due to its absence of brown eye pigment. The red pigment is located on the X chromosome. The synthesis of brown pigment is due to the process of converting tryptophane to kynurenine, vermilion flies lack the ability to convert these amino acids blocking the production of brown pigment. The reduction in the amount of tryptophan converted to kynurenine in vermilion mutants has been associated with longer life spans in comparison to wild-type flies.Drosophila melanogaster_item_2_25

Drosophila melanogaster_unordered_list_3

  • vg: vestigial- A spontaneous mutation, discovered in 1919 by Thomas Morgan and Calvin Bridges. Vestigial wings are those not fully developed and that have lost function. Since the discovery of the vestigial gene in Drosophila melanogaster, there have been many discoveries of the vestigial gene in other vertebrates and their functions within the vertebrates. The vestigial gene is considered to be one of the most important genes for wing formation, but when it becomes over expressed the issue of ectopic wings begin to form. The vestigial gene acts to regulate the expression of the wing imaginal discs in the embryo and acts with other genes to regulate the development of the wings. A mutated vestigial allele removes an essential sequence of the DNA required for correct development of the wings.Drosophila melanogaster_item_3_26
  • w: white- Drosophila melanogaster wild type typically expresses a brick red eye color. The white eye mutation in fruit flies is caused due to the absence of two pigments associated with red and brown eye colors; peridines (red) and ommochromes (brown). In January 1910, Thomas Hunt Morgan first discovered the white gene and denoted it as w. The discovery of the white-eye mutation by Morgan brought about the beginnings of genetic experimentation and analysis of Drosophila melanogaster. Hunt eventually discovered that the gene followed a similar pattern of inheritance related to the meiotic segregation of the X chromosome. He discovered that the gene was located on the X chromosome with this information. This led to the discovery of sex-linked genes and also to the discovery of other mutations in Drosophila melanogaster. The white-eye mutation leads to several disadvantages in flies, such as a reduced climbing ability, shortened life span, and lowered resistance to stress when compared to wild type flies. Drosophila melanogaster has a series of mating behaviors that enable them to copulate within a given environment and therefore contribute to their fitness. After Morgan’s discovery of the white-eye mutation being sex-linked, a study lead by Sturtevant (1915) concluded that white-eyed males were less successful than wild-type males in terms of mating with females. It was found that the greater the density in eye pigmentation, the greater the success in mating for the males of Drosophila melanogaster.Drosophila melanogaster_item_3_27
  • y: yellow- The yellow gene is a genetic mutation known as Dmel\y within the widely used data base called flybase. This mutation can be easily identified by the atypical yellow pigment observed in the cuticle of the adult flies and the mouth pieces of the larva. The y mutation comprises the following phenotypic classes: the mutants that show a complete loss of pigmentation from the cuticle (y-type) and other mutants that show a mosaic pigment pattern with some regions of the cuticle (wild type, y2-type). The role of the yellow gene is diverse and is responsible for changes in behaviour, sex-specific reproductive maturation and, epigenetic reprogramming. The y gene is an ideal gene to study as it is visibly clear when an organisim has this gene, making it easier to understand the passage of DNA to offspring.Drosophila melanogaster_item_3_28

Genome Drosophila melanogaster_section_10

Drosophila melanogaster_table_infobox_1

Genomic informationDrosophila melanogaster_table_caption_1
NCBI genome IDDrosophila melanogaster_header_cell_1_0_0 Drosophila melanogaster_cell_1_0_1
PloidyDrosophila melanogaster_header_cell_1_1_0 diploidDrosophila melanogaster_cell_1_1_1
Number of chromosomesDrosophila melanogaster_header_cell_1_2_0 8Drosophila melanogaster_cell_1_2_1
Year of completionDrosophila melanogaster_header_cell_1_3_0 2015Drosophila melanogaster_cell_1_3_1

The genome of D. melanogaster (sequenced in 2000, and curated at the FlyBase database) contains four pairs of chromosomes – an X/Y pair, and three autosomes labeled 2, 3, and 4. Drosophila melanogaster_sentence_100

The fourth chromosome is so tiny, it is often ignored, aside from its important eyeless gene. Drosophila melanogaster_sentence_101

The D. melanogaster sequenced genome of 139.5 million base pairs has been annotated and contains around 15,682 genes according to Ensemble release 73. Drosophila melanogaster_sentence_102

More than 60% of the genome appears to be functional non-protein-coding DNA involved in gene expression control. Drosophila melanogaster_sentence_103

Determination of sex in Drosophila occurs by the X:A ratio of X chromosomes to autosomes, not because of the presence of a Y chromosome as in human sex determination. Drosophila melanogaster_sentence_104

Although the Y chromosome is entirely heterochromatic, it contains at least 16 genes, many of which are thought to have male-related functions. Drosophila melanogaster_sentence_105

Similarity to humans Drosophila melanogaster_section_11

A March 2000 study by National Human Genome Research Institute comparing the fruit fly and human genome estimated that about 60% of genes are conserved between the two species. Drosophila melanogaster_sentence_106

About 75% of known human disease genes have a recognizable match in the genome of fruit flies, and 50% of fly protein sequences have mammalian homologs. Drosophila melanogaster_sentence_107

An online database called Homophila is available to search for human disease gene homologues in flies and vice versa. Drosophila melanogaster_sentence_108

Drosophila is being used as a genetic model for several human diseases including the neurodegenerative disorders Parkinson's, Huntington's, spinocerebellar ataxia and Alzheimer's disease. Drosophila melanogaster_sentence_109

The fly is also being used to study mechanisms underlying aging and oxidative stress, immunity, diabetes, and cancer, as well as drug abuse. Drosophila melanogaster_sentence_110

Connectome Drosophila melanogaster_section_12

Drosophila is one of the few animals (C. Drosophila melanogaster_sentence_111 elegans being another) where detailed neural circuits (a connectome) are available. Drosophila melanogaster_sentence_112

A high-level connectome, at the level of brain compartments and interconnecting tracts of neurons, exists for the full fly brain. Drosophila melanogaster_sentence_113

A version of this is available online. Drosophila melanogaster_sentence_114

Detailed circuit-level connectomes exist for the lamina and a medulla column, both in the visual system of the fruit fly, and the alpha lobe of the mushroom body. Drosophila melanogaster_sentence_115

In May 2017 a paper published in bioRxiv presented an electron microscopy image stack of the whole adult female brain at synaptic resolution. Drosophila melanogaster_sentence_116

The volume is available for sparse tracing of selected circuits. Drosophila melanogaster_sentence_117

In 2020, a dense connectome of half the central brain of Drosophila was released, along with a web site that allows queries and exploration of this data. Drosophila melanogaster_sentence_118

The methods used in reconstruction and initial analysis of the connectome followed. Drosophila melanogaster_sentence_119

Development Drosophila melanogaster_section_13

Main article: Drosophila embryogenesis Drosophila melanogaster_sentence_120

The life cycle of this insect has four stages: fertilized egg, larva, pupa, and adult. Drosophila melanogaster_sentence_121

Embryogenesis in Drosophila has been extensively studied, as its small size, short generation time, and large brood size makes it ideal for genetic studies. Drosophila melanogaster_sentence_122

It is also unique among model organisms in that cleavage occurs in a syncytium. Drosophila melanogaster_sentence_123

During oogenesis, cytoplasmic bridges called "ring canals" connect the forming oocyte to nurse cells. Drosophila melanogaster_sentence_124

Nutrients and developmental control molecules move from the nurse cells into the oocyte. Drosophila melanogaster_sentence_125

In the figure to the left, the forming oocyte can be seen to be covered by follicular support cells. Drosophila melanogaster_sentence_126

After fertilization of the oocyte, the early embryo (or syncytial embryo) undergoes rapid DNA replication and 13 nuclear divisions until about 5000 to 6000 nuclei accumulate in the unseparated cytoplasm of the embryo. Drosophila melanogaster_sentence_127

By the end of the eighth division, most nuclei have migrated to the surface, surrounding the yolk sac (leaving behind only a few nuclei, which will become the yolk nuclei). Drosophila melanogaster_sentence_128

After the 10th division, the pole cells form at the posterior end of the embryo, segregating the germ line from the syncytium. Drosophila melanogaster_sentence_129

Finally, after the 13th division, cell membranes slowly invaginate, dividing the syncytium into individual somatic cells. Drosophila melanogaster_sentence_130

Once this process is completed, gastrulation starts. Drosophila melanogaster_sentence_131

Nuclear division in the early Drosophila embryo happens so quickly, no proper checkpoints exist, so mistakes may be made in division of the DNA. Drosophila melanogaster_sentence_132

To get around this problem, the nuclei that have made a mistake detach from their centrosomes and fall into the centre of the embryo (yolk sac), which will not form part of the fly. Drosophila melanogaster_sentence_133

The gene network (transcriptional and protein interactions) governing the early development of the fruit fly embryo is one of the best understood gene networks to date, especially the patterning along the anteroposterior (AP) and dorsoventral (DV) axes (See under morphogenesis). Drosophila melanogaster_sentence_134

The embryo undergoes well-characterized morphogenetic movements during gastrulation and early development, including germ-band extension, formation of several furrows, ventral invagination of the mesoderm, and posterior and anterior invagination of endoderm (gut), as well as extensive body segmentation until finally hatching from the surrounding cuticle into a first-instar larva. Drosophila melanogaster_sentence_135

During larval development, tissues known as imaginal discs grow inside the larva. Drosophila melanogaster_sentence_136

Imaginal discs develop to form most structures of the adult body, such as the head, legs, wings, thorax, and genitalia. Drosophila melanogaster_sentence_137

Cells of the imaginal disks are set aside during embryogenesis and continue to grow and divide during the larval stages—unlike most other cells of the larva, which have differentiated to perform specialized functions and grow without further cell division. Drosophila melanogaster_sentence_138

At metamorphosis, the larva forms a pupa, inside which the larval tissues are reabsorbed and the imaginal tissues undergo extensive morphogenetic movements to form adult structures. Drosophila melanogaster_sentence_139

Developmental plasticity Drosophila melanogaster_section_14

Biotic and abiotic factors experienced during development will affect developmental resource allocation leading to phenotypic variation, also referred to as developmental plasticity. Drosophila melanogaster_sentence_140

As in all insects, environmental factors can influence several aspects of development in Drosophila melanogaster. Drosophila melanogaster_sentence_141

Fruit flies reared under a hypoxia treatment experience decreased thorax length, while hyperoxia produces smaller flight muscles, suggesting negative developmental effects of extreme oxygen levels. Drosophila melanogaster_sentence_142

Circadian rhythms are also subject to developmental plasticity. Drosophila melanogaster_sentence_143

Light conditions during development affect daily activity patterns in Drosophila melanogaster, where flies raised under constant dark or light are less active as adults than those raised under a 12-hour light/dark cycle. Drosophila melanogaster_sentence_144

Temperature is one of the most pervasive factors influencing arthropod development. Drosophila melanogaster_sentence_145

In Drosophila melanogaster temperature-induced developmental plasticity can be beneficial and/or detrimental. Drosophila melanogaster_sentence_146

Most often lower developmental temperatures reduce growth rates which influence many other physiological factors. Drosophila melanogaster_sentence_147

For example, development at 25 °C increases walking speed, , and territorial success, while development at 18 °C increases body mass, wing size, all of which are tied to fitness. Drosophila melanogaster_sentence_148

Moreover, developing at certain low temperatures produces proportionally large wings which improve flight and reproductive performance at similarly low temperatures (See acclimation). Drosophila melanogaster_sentence_149

While certain effects of developmental temperature, like body size, are irreversible in ectotherms, others can be reversible. Drosophila melanogaster_sentence_150

When Drosophila melanogaster develop at cold temperatures they will have greater cold tolerance, but if cold-reared flies are maintained at warmer temperatures their cold tolerance decreases and heat tolerance increases over time. Drosophila melanogaster_sentence_151

Because insects typically only mate in a specific range of temperatures, their cold/heat tolerance is an important trait in maximizing reproductive output. Drosophila melanogaster_sentence_152

While the traits described above are expected to manifest similarly across sexes, developmental temperature can also produce sex-specific effects in D. melanogaster adults. Drosophila melanogaster_sentence_153

Drosophila melanogaster_unordered_list_4

  • Females- Ovariole number is significantly affected by developmental temperature in D. melanogaster. Egg size is also affected by developmental temperature, and exacerbated when both parents develop at warm temperatures (See Maternal effect). Under stressful temperatures, these structures will develop to smaller ultimate sizes and decrease a female's reproductive output. Early fecundity (total eggs laid in first 10 days post-eclosion) is maximized when reared at 25 °C (versus 17 °C and 29 °C) regardless of adult temperature. Across a wide range of developmental temperatures, females tend to have greater heat tolerance than males.Drosophila melanogaster_item_4_29
  • Males- Stressful developmental temperatures will cause sterility in D. melanogaster males; although the upper temperature limit can be increased by maintaining strains at high temperatures (See acclimation). Male sterility can be reversible if adults are returned to an optimal temperature after developing at stressful temperatures. Male flies are smaller and more successful at defending food/oviposition sites when reared at 25 °C versus 18 °C; thus smaller males will have increased mating success and reproductive output.Drosophila melanogaster_item_4_30

Sex determination Drosophila melanogaster_section_15

Drosophila flies have both X and Y chromosomes, as well as autosomes. Drosophila melanogaster_sentence_154

Unlike humans, the Y chromosome does not confer maleness; rather, it encodes genes necessary for making sperm. Drosophila melanogaster_sentence_155

Sex is instead determined by the ratio of X chromosomes to autosomes. Drosophila melanogaster_sentence_156

Furthermore, each cell "decides" whether to be male or female independently of the rest of the organism, resulting in the occasional occurrence of gynandromorphs. Drosophila melanogaster_sentence_157

Drosophila melanogaster_table_general_2

X ChromosomesDrosophila melanogaster_header_cell_2_0_0 AutosomesDrosophila melanogaster_header_cell_2_0_1 Ratio of X:ADrosophila melanogaster_header_cell_2_0_2 SexDrosophila melanogaster_header_cell_2_0_3
XXXXDrosophila melanogaster_cell_2_1_0 AAAADrosophila melanogaster_cell_2_1_1 1Drosophila melanogaster_cell_2_1_2 Normal FemaleDrosophila melanogaster_cell_2_1_3
XXXDrosophila melanogaster_cell_2_2_0 AAADrosophila melanogaster_cell_2_2_1 1Drosophila melanogaster_cell_2_2_2 Normal FemaleDrosophila melanogaster_cell_2_2_3
XXYDrosophila melanogaster_cell_2_3_0 AADrosophila melanogaster_cell_2_3_1 1Drosophila melanogaster_cell_2_3_2 Normal FemaleDrosophila melanogaster_cell_2_3_3
XXYYDrosophila melanogaster_cell_2_4_0 AADrosophila melanogaster_cell_2_4_1 1Drosophila melanogaster_cell_2_4_2 Normal FemaleDrosophila melanogaster_cell_2_4_3
XXDrosophila melanogaster_cell_2_5_0 AADrosophila melanogaster_cell_2_5_1 1Drosophila melanogaster_cell_2_5_2 Normal FemaleDrosophila melanogaster_cell_2_5_3
XYDrosophila melanogaster_cell_2_6_0 AADrosophila melanogaster_cell_2_6_1 0.50Drosophila melanogaster_cell_2_6_2 Normal MaleDrosophila melanogaster_cell_2_6_3
XDrosophila melanogaster_cell_2_7_0 AADrosophila melanogaster_cell_2_7_1 0.50Drosophila melanogaster_cell_2_7_2 Normal Male (sterile)Drosophila melanogaster_cell_2_7_3
XXXDrosophila melanogaster_cell_2_8_0 AADrosophila melanogaster_cell_2_8_1 1.50Drosophila melanogaster_cell_2_8_2 MetafemaleDrosophila melanogaster_cell_2_8_3
XXXXDrosophila melanogaster_cell_2_9_0 AAADrosophila melanogaster_cell_2_9_1 1.33Drosophila melanogaster_cell_2_9_2 MetafemaleDrosophila melanogaster_cell_2_9_3
XXDrosophila melanogaster_cell_2_10_0 AAADrosophila melanogaster_cell_2_10_1 0.66Drosophila melanogaster_cell_2_10_2 IntersexDrosophila melanogaster_cell_2_10_3
XDrosophila melanogaster_cell_2_11_0 AAADrosophila melanogaster_cell_2_11_1 0.33Drosophila melanogaster_cell_2_11_2 MetamaleDrosophila melanogaster_cell_2_11_3

Three major genes are involved in determination of Drosophila sex. Drosophila melanogaster_sentence_158

These are sex-lethal, sisterless, and deadpan. Drosophila melanogaster_sentence_159

Deadpan is an autosomal gene which inhibits sex-lethal, while sisterless is carried on the X chromosome and inhibits the action of deadpan. Drosophila melanogaster_sentence_160

An AAX cell has twice as much deadpan as sisterless, so sex-lethal will be inhibited, creating a male. Drosophila melanogaster_sentence_161

However, an AAXX cell will produce enough sisterless to inhibit the action of deadpan, allowing the sex-lethal gene to be transcribed to create a female. Drosophila melanogaster_sentence_162

Later, control by deadpan and sisterless disappears and what becomes important is the form of the sex-lethal gene. Drosophila melanogaster_sentence_163

A secondary promoter causes transcription in both males and females. Drosophila melanogaster_sentence_164

Analysis of the cDNA has shown that different forms are expressed in males and females. Drosophila melanogaster_sentence_165

Sex-lethal has been shown to affect the splicing of its own mRNA. Drosophila melanogaster_sentence_166

In males, the third exon is included which encodes a stop codon, causing a truncated form to be produced. Drosophila melanogaster_sentence_167

In the female version, the presence of sex-lethal causes this exon to be missed out; the other seven amino acids are produced as a full peptide chain, again giving a difference between males and females. Drosophila melanogaster_sentence_168

Presence or absence of functional sex-lethal proteins now go on to affect the transcription of another protein known as doublesex. Drosophila melanogaster_sentence_169

In the absence of sex-lethal, doublesex will have the fourth exon removed and be translated up to and including exon 6 (DSX-M[ale]), while in its presence the fourth exon which encodes a stop codon will produce a truncated version of the protein (DSX-F[emale]). Drosophila melanogaster_sentence_170

DSX-F causes transcription of Yolk proteins 1 and 2 in somatic cells, which will be pumped into the oocyte on its production. Drosophila melanogaster_sentence_171

Immunity Drosophila melanogaster_section_16

The D. melanogaster immune system can be divided into two responses: humoral and cell-mediated. Drosophila melanogaster_sentence_172

The former is a systemic response mediated in large part through the Toll and Imd pathways, which are parallel systems for detecting microbes. Drosophila melanogaster_sentence_173

Other pathways including the stress response pathways JAK-STAT and P38, nutritional signalling via FOXO, and JNK cell death signalling are all involved in key physiological responses to infection. Drosophila melanogaster_sentence_174

D. melanogaster has a fat body, which is analogous to the human liver. Drosophila melanogaster_sentence_175

The fat body is the primary secretory organ and produces key immune molecules upon infection, such as serine proteases and antimicrobial peptides (AMPs). Drosophila melanogaster_sentence_176

AMPs are secreted into the hemolymph and bind infectious bacteria and fungi, killing them by forming pores in their cell walls or inhibiting intracellular processes. Drosophila melanogaster_sentence_177

The cellular immune response instead refers to the direct activity of blood cells (hemocytes) in Drosophila, which are analogous to mammalian monocytes/macrophages. Drosophila melanogaster_sentence_178

Hemocytes also possess a significant role in mediating humoral immune responses such as the melanization reaction. Drosophila melanogaster_sentence_179

The immune response to infection can involve up to 2,423 genes, or 13.7% of the genome. Drosophila melanogaster_sentence_180

Although the fly's transcriptional response to microbial challenge is highly specific to individual pathogens, Drosophila differentially expresses a core group of 252 genes upon infection with most bacteria. Drosophila melanogaster_sentence_181

This core group of genes is associated with gene ontology categories such as antimicrobial response, stress response, secretion, neuron-like, reproduction, and metabolism among others. Drosophila melanogaster_sentence_182

Drosophila also possesses several immune mechanisms to both shape the microbiota and prevent excessive immune responses upon detection of microbial stimuli. Drosophila melanogaster_sentence_183

For instance, secreted PGRPs with amidase activity scavenge and degrade immunostimulatory DAP-type PGN in order to block Imd activation. Drosophila melanogaster_sentence_184

Unlike mammals, Drosophila have innate immunity but lack an adaptive immune response. Drosophila melanogaster_sentence_185

However, the core elements of this innate immune response are conserved between humans and fruit flies. Drosophila melanogaster_sentence_186

As a result, the fruit fly offers a useful model of innate immunity for disentangling genetic interactions of signalling and effector function, as flies do not have to contend with interference of adaptive immune mechanisms that could confuse results. Drosophila melanogaster_sentence_187

Various genetic tools, protocols, and assays make Drosophila a classical model for studying the innate immune system, which has even included immune research on the international space station. Drosophila melanogaster_sentence_188

The Drosophila Toll pathway Drosophila melanogaster_section_17

The first description of Toll-like receptors involved in the response to infection was performed in Drosophila. Drosophila melanogaster_sentence_189

culminating in a Nobel prize in 2011. Drosophila melanogaster_sentence_190

The Toll pathway in Drosophila is homologous to Toll-like pathways in mammals. Drosophila melanogaster_sentence_191

This regulatory cascade is initiated following pathogen recognition by pattern recognition receptors, particularly of Gram-positive bacteria, parasites, and fungal infection. Drosophila melanogaster_sentence_192

This activation leads to serine protease signalling cascades ultimately activating the cytokine Spätzle. Drosophila melanogaster_sentence_193

Alternatively, microbial proteases can directly cleave serine proteases like Persephone that then propagate signalling. Drosophila melanogaster_sentence_194

The cytokine Spatzle then acts as the ligand for the Toll pathway in flies. Drosophila melanogaster_sentence_195

Upon infection, pro-Spatzle is cleaved by the protease SPE (Spatzle processing enzyme) to become active Spatzle, which binds to the Toll receptor located on the cell surface of the fat body and dimerizes for activation of downstream NF-κB signaling pathways, including multiple death domain containing proteins and negative regulators such as the ankyrin repeat protein Cactus. Drosophila melanogaster_sentence_196

The pathway culminates with the translocation of the NF-κB transcription factors Dorsal and Dif (Dorsal-related immunity factor) into the nucleus. Drosophila melanogaster_sentence_197

The Toll pathway was identified by its regulation of antimicrobial peptides (AMPs), including the antifungal peptide Drosomycin. Drosophila melanogaster_sentence_198

Upon infection, AMPs increase in expression sometimes by 1000-fold, providing unmistakable readouts of pathway activation. Drosophila melanogaster_sentence_199

Another group of Toll-regulated AMP-like effectors includes the Bomanins, which appear to be responsible for the bulk of Toll-mediated immune defence, however Bomanins alone do not exhibit antimicrobial activity. Drosophila melanogaster_sentence_200

It has been proposed that a second SPE-like enzyme similarly acts to activate Spatzle, as loss of SPE does not completely reduce the activity of Toll signalling, however no second SPE has yet been identified. Drosophila melanogaster_sentence_201

A number of serine proteases are yet to be characterized, including many with homology to SPE. Drosophila melanogaster_sentence_202

The Toll pathway also interacts with renal filtration of microbiota-derived peptidoglycan, maintaining immune homeostasis. Drosophila melanogaster_sentence_203

Mechanistically, nephrocytes endocytose Lys-type PGN from systemic circulation and route it to lysosomes for degradation. Drosophila melanogaster_sentence_204

Without this, Toll signalling is constitutively activated, resulting in a severe drain on nutrient reserves and a significant stress on host physiology. Drosophila melanogaster_sentence_205

The Drosophila Imd pathway Drosophila melanogaster_section_18

The Imd pathway is orthologous to human TNF receptor superfamily signalling, and is triggered by Gram-negative bacteria through recognition by peptidoglycan recognition proteins (PGRP) including both soluble receptors and cell surface receptors (PGRP-LE and LC, respectively). Drosophila melanogaster_sentence_206

Imd signalling culminates in the translocation of the NF-κB transcription factor Relish into the nucleus, leading to the upregulation of Imd-responsive genes including the AMP Diptericin. Drosophila melanogaster_sentence_207

Consequently, flies deficient for AMPs resemble Imd pathway mutants in terms of susceptibility to bacterial infection. Drosophila melanogaster_sentence_208

Imd signalling and Relish specifically are also involved in the regulation of immunity at surface epithelia including in the gut and respiratory tracts. Drosophila melanogaster_sentence_209

The Relish transcription factor has also been implicated in processes regarding cell proliferation and neurodegeneration either through autophagy, or autoimmune toxicity. Drosophila melanogaster_sentence_210

In neurodegenerative models relying on Imd signalling, expression of AMPs in the brain is correlated with brain tissue damage, lesions, and ultimately death. Drosophila melanogaster_sentence_211

Relish-regulated AMPs such as Defensin and Diptericin also have anti-cancer properties promoting tumour clearance. Drosophila melanogaster_sentence_212

The Imd-regulated AMP Diptericin B is also produced by the fat body specifically in the head, and Diptericin B is required for long-term memory formation. Drosophila melanogaster_sentence_213

JAK-STAT signalling Drosophila melanogaster_section_19

Multiple elements of the Drosophila JAK-STAT signalling pathway bear direct homology to human JAK-STAT pathway genes. Drosophila melanogaster_sentence_214

JAK-STAT signalling is induced upon various organismal stresses such as heat stress, dehydration, or infection. Drosophila melanogaster_sentence_215

JAK-STAT induction leads to the production of a number of stress response proteins including Thioester-containing proteins (TEPs), Turandots, and the putative antimicrobial peptide Listericin. Drosophila melanogaster_sentence_216

The mechanisms through which many of these proteins act is still under investigation. Drosophila melanogaster_sentence_217

For instance, the TEPs appear to promote phagocytosis of Gram-positive bacteria and the induction of the Toll pathway. Drosophila melanogaster_sentence_218

As a consequence, flies lacking TEPs are susceptible to infection by Toll pathway challenges. Drosophila melanogaster_sentence_219

The Cellular response to infection Drosophila melanogaster_section_20

Circulating hemocytes are key regulators of infection. Drosophila melanogaster_sentence_220

This has been demonstrated both through genetic tools to generate flies lacking hemocytes, or through injecting microglass beads or lipid droplets that saturate hemocyte ability to phagocytose a secondary infection. Drosophila melanogaster_sentence_221

Flies treated like this fail to phagocytose bacteria upon infection, and are correspondingly susceptible to infection. Drosophila melanogaster_sentence_222

These hemocytes derive from two waves of hematopoiesis, one occurring in the early embryo and one occurring during development from larva to adult. Drosophila melanogaster_sentence_223

However Drosophila hemocytes do not renew over the adult lifespan, and so the fly has a finite number of hemocytes that decrease over the course of its lifespan. Drosophila melanogaster_sentence_224

Hemocytes are also involved in regulating cell-cycle events and apoptosis of aberrant tissue (e.g. cancerous cells) by producing Eiger, a tumor necrosis factor signalling molecule that promotes JNK signalling and ultimately cell death and apoptosis. Drosophila melanogaster_sentence_225

Behavioral genetics and neuroscience Drosophila melanogaster_section_21

In 1971, Ron Konopka and Seymour Benzer published "Clock mutants of Drosophila melanogaster", a paper describing the first mutations that affected an animal's behavior. Drosophila melanogaster_sentence_226

Wild-type flies show an activity rhythm with a frequency of about a day (24 hours). Drosophila melanogaster_sentence_227

They found mutants with faster and slower rhythms, as well as broken rhythms—flies that move and rest in random spurts. Drosophila melanogaster_sentence_228

Work over the following 30 years has shown that these mutations (and others like them) affect a group of genes and their products that form a biochemical or biological clock. Drosophila melanogaster_sentence_229

This clock is found in a wide range of fly cells, but the clock-bearing cells that control activity are several dozen neurons in the fly's central brain. Drosophila melanogaster_sentence_230

Since then, Benzer and others have used behavioral screens to isolate genes involved in vision, olfaction, audition, learning/memory, courtship, pain, and other processes, such as longevity. Drosophila melanogaster_sentence_231

Following the pioneering work of Alfred Henry Sturtevant and others, Benzer and colleagues used sexual mosaics to develop a novel fate mapping technique. Drosophila melanogaster_sentence_232

This technique made it possible to assign a particular characteristic to a specific anatomical location. Drosophila melanogaster_sentence_233

For example, this technique showed that male courtship behavior is controlled by the brain. Drosophila melanogaster_sentence_234

Mosaic fate mapping also provided the first indication of the existence of pheromones in this species. Drosophila melanogaster_sentence_235

Males distinguish between conspecific males and females and direct persistent courtship preferentially toward females thanks to a female-specific sex pheromone which is mostly produced by the female's tergites. Drosophila melanogaster_sentence_236

The first learning and memory mutants (dunce, rutabaga, etc.) were isolated by William "Chip" Quinn while in Benzer's lab, and were eventually shown to encode components of an intracellular signaling pathway involving cyclic AMP, protein kinase A, and a transcription factor known as CREB. Drosophila melanogaster_sentence_237

These molecules were shown to be also involved in synaptic plasticity in Aplysia and mammals. Drosophila melanogaster_sentence_238

The Nobel Prize in Physiology or Medicine for 2017 was awarded to Jeffrey C. Hall, Michael Rosbash, Michael W. Young for their works using fruit flies in understanding the "molecular mechanisms controlling the circadian rhythm". Drosophila melanogaster_sentence_239

Male flies sing to the females during courtship using their wings to generate sound, and some of the genetics of sexual behavior have been characterized. Drosophila melanogaster_sentence_240

In particular, the fruitless gene has several different splice forms, and male flies expressing female splice forms have female-like behavior and vice versa. Drosophila melanogaster_sentence_241

The TRP channels nompC, nanchung, and inactive are expressed in sound-sensitive Johnston's organ neurons and participate in the transduction of sound. Drosophila melanogaster_sentence_242

Mutating the Genderblind gene, also known as CG6070, alters the sexual behavior of Drosophila, turning the flies bisexual. Drosophila melanogaster_sentence_243

Flies use a modified version of Bloom filters to detect novelty of odors, with additional features including similarity of novel odor to that of previously experienced examples, and time elapsed since previous experience of the same odor. Drosophila melanogaster_sentence_244

Aggression Drosophila melanogaster_section_22

As with most insects, aggressive behaviors between male flies commonly occur in the presence of courting a female and when competing for resources. Drosophila melanogaster_sentence_245

Such behaviors often involve raising wings and legs towards the opponent and attacking with the whole body. Drosophila melanogaster_sentence_246

Thus, it often causes wing damage, which reduces their fitness by removing their ability to fly and mate. Drosophila melanogaster_sentence_247

Acoustic communication Drosophila melanogaster_section_23

In order for aggression to occur, male flies produce sounds to communicate their intent. Drosophila melanogaster_sentence_248

A 2017 study found that songs promoting aggression contain pulses occurring at longer intervals. Drosophila melanogaster_sentence_249

RNA sequencing from fly mutants displaying over-aggressive behaviors found more than 50 auditory-related genes (important for transient receptor potentials, Ca signaling, and mechanoreceptor potentials) to be upregulated in the AB neurons located in Johnston's organ. Drosophila melanogaster_sentence_250

In addition, aggression levels were reduced when these genes were knocked out via RNA interference. Drosophila melanogaster_sentence_251

This signifies the major role of hearing as a sensory modality in communicating aggression. Drosophila melanogaster_sentence_252

Pheromone signaling Drosophila melanogaster_section_24

Other than hearing, another sensory modality that regulates aggression is pheromone signaling, which operates through either the olfactory system or the gustatory system depending on the pheromone. Drosophila melanogaster_sentence_253

An example is cVA, an anti-aphrodisiac pheromone used by males to mark females after copulation and to deter other males from mating. Drosophila melanogaster_sentence_254

This male-specific pheromone causes an increase in male-male aggression when detected by another male's gustatory system. Drosophila melanogaster_sentence_255

However, upon inserting a mutation that makes the flies irresponsive to cVA, no aggressive behaviors were seen. Drosophila melanogaster_sentence_256

This shows how there are multiple modalities for promoting aggression in flies. Drosophila melanogaster_sentence_257

Competition for food Drosophila melanogaster_section_25

Specifically, when competing for food, aggression occurs based on amount of food available and is independent of any social interactions between males. Drosophila melanogaster_sentence_258

Specifically, sucrose was found to stimulate gustatory receptor neurons, which was necessary to stimulate aggression. Drosophila melanogaster_sentence_259

However, once the amount of food becomes greater than a certain amount, the competition between males lowers. Drosophila melanogaster_sentence_260

This is possibly due to an over-abundance of food resources. Drosophila melanogaster_sentence_261

On a larger scale, food was found to determine the boundaries of a territory since flies were observed to be more aggressive at the food's physical perimeter. Drosophila melanogaster_sentence_262

Effect of sleep deprivation Drosophila melanogaster_section_26

However, like most behaviors requiring arousal and wakefulness, aggression was found to be impaired via sleep deprivation. Drosophila melanogaster_sentence_263

Specifically, this occurs through the impairment of Octopamine and dopamine signaling, which are important pathways for regulating arousal in insects. Drosophila melanogaster_sentence_264

Due to reduced aggression, sleep-deprived male flies were found to be disadvantaged at mating compared to normal flies. Drosophila melanogaster_sentence_265

However, when octopamine agonists were administered upon these sleep-deprived flies, aggression levels were seen to be increased and sexual fitness was subsequently restored. Drosophila melanogaster_sentence_266

Therefore, this finding implicates the importance of sleep in aggression between male flies. Drosophila melanogaster_sentence_267

Transgenesis Drosophila melanogaster_section_27

It is now relatively simple to generate transgenic flies in Drosophila, relying on a variety of techniques. Drosophila melanogaster_sentence_268

One approach of inserting foreign genes into the Drosophila genome involves P elements. Drosophila melanogaster_sentence_269

The transposable P elements, also known as transposons, are segments of bacterial DNA that are transferred into the fly genome. Drosophila melanogaster_sentence_270

Transgenic flies have already contributed to many scientific advances, e.g., modeling such human diseases as Parkinson's, neoplasia, obesity, and diabetes. Drosophila melanogaster_sentence_271

Vision Drosophila melanogaster_section_28

The compound eye of the fruit fly contains 760 unit eyes or ommatidia, and are one of the most advanced among insects. Drosophila melanogaster_sentence_272

Each ommatidium contains eight photoreceptor cells (R1-8), support cells, pigment cells, and a cornea. Drosophila melanogaster_sentence_273

Wild-type flies have reddish pigment cells, which serve to absorb excess blue light so the fly is not blinded by ambient light. Drosophila melanogaster_sentence_274

Eye color genes regulate cellular vesicular transport. Drosophila melanogaster_sentence_275

The enzymes needed for pigment synthesis are then transported to the cell's pigment granule, which holds pigment precursor molecules. Drosophila melanogaster_sentence_276

Each photoreceptor cell consists of two main sections, the cell body and the rhabdomere. Drosophila melanogaster_sentence_277

The cell body contains the nucleus, while the 100-μm-long rhabdomere is made up of toothbrush-like stacks of membrane called microvilli. Drosophila melanogaster_sentence_278

Each microvillus is 1–2 μm in length and about 60 nm in diameter. Drosophila melanogaster_sentence_279

The membrane of the rhabdomere is packed with about 100 million rhodopsin molecules, the visual protein that absorbs light. Drosophila melanogaster_sentence_280

The rest of the visual proteins are also tightly packed into the microvillar space, leaving little room for cytoplasm. Drosophila melanogaster_sentence_281

The photoreceptors in Drosophila express a variety of rhodopsin isoforms. Drosophila melanogaster_sentence_282

The R1-R6 photoreceptor cells express rhodopsin1 (Rh1), which absorbs blue light (480 nm). Drosophila melanogaster_sentence_283

The R7 and R8 cells express a combination of either Rh3 or Rh4, which absorb UV light (345 nm and 375 nm), and Rh5 or Rh6, which absorb blue (437 nm) and green (508 nm) light, respectively. Drosophila melanogaster_sentence_284

Each rhodopsin molecule consists of an opsin protein covalently linked to a carotenoid chromophore, 11-cis-3-hydroxyretinal. Drosophila melanogaster_sentence_285

As in vertebrate vision, visual transduction in invertebrates occurs via a G protein-coupled pathway. Drosophila melanogaster_sentence_286

However, in vertebrates, the G protein is transducin, while the G protein in invertebrates is Gq (dgq in Drosophila). Drosophila melanogaster_sentence_287

When rhodopsin (Rh) absorbs a photon of light its chromophore, 11-cis-3-hydroxyretinal, is isomerized to all-trans-3-hydroxyretinal. Drosophila melanogaster_sentence_288

Rh undergoes a conformational change into its active form, metarhodopsin. Drosophila melanogaster_sentence_289

Metarhodopsin activates Gq, which in turn activates a phospholipase Cβ (PLCβ) known as NorpA. Drosophila melanogaster_sentence_290

PLCβ hydrolyzes phosphatidylinositol (4,5)-bisphosphate (PIP2), a phospholipid found in the cell membrane, into soluble inositol triphosphate (IP3) and diacylglycerol (DAG), which stays in the cell membrane. Drosophila melanogaster_sentence_291

DAG or a derivative of DAG causes a calcium-selective ion channel known as transient receptor potential (TRP) to open and calcium and sodium flows into the cell. Drosophila melanogaster_sentence_292

IP3 is thought to bind to IP3 receptors in the subrhabdomeric cisternae, an extension of the endoplasmic reticulum, and cause release of calcium, but this process does not seem to be essential for normal vision. Drosophila melanogaster_sentence_293

Calcium binds to proteins such as calmodulin (CaM) and an eye-specific protein kinase C (PKC) known as InaC. Drosophila melanogaster_sentence_294

These proteins interact with other proteins and have been shown to be necessary for shut off of the light response. Drosophila melanogaster_sentence_295

In addition, proteins called arrestins bind metarhodopsin and prevent it from activating more Gq. Drosophila melanogaster_sentence_296

A sodium-calcium exchanger known as CalX pumps the calcium out of the cell. Drosophila melanogaster_sentence_297

It uses the inward sodium gradient to export calcium at a stoichiometry of 3 Na/ 1 Ca. Drosophila melanogaster_sentence_298

TRP, InaC, and PLC form a signaling complex by binding a scaffolding protein called InaD. Drosophila melanogaster_sentence_299

InaD contains five binding domains called PDZ domain proteins, which specifically bind the C termini of target proteins. Drosophila melanogaster_sentence_300

Disruption of the complex by mutations in either the PDZ domains or the target proteins reduces the efficiency of signaling. Drosophila melanogaster_sentence_301

For example, disruption of the interaction between InaC, the protein kinase C, and InaD results in a delay in inactivation of the light response. Drosophila melanogaster_sentence_302

Unlike vertebrate metarhodopsin, invertebrate metarhodopsin can be converted back into rhodopsin by absorbing a photon of orange light (580 nm). Drosophila melanogaster_sentence_303

About two-thirds of the Drosophila brain is dedicated to visual processing. Drosophila melanogaster_sentence_304

Although the spatial resolution of their vision is significantly worse than that of humans, their temporal resolution is around 10 times better. Drosophila melanogaster_sentence_305

Grooming Drosophila melanogaster_section_29

Drosophila are known to exhibit grooming behaviors that are executed in a predictable manner. Drosophila melanogaster_sentence_306

Drosophila consistently begin a grooming sequence by using their front legs to clean the eyes, then the head and antennae. Drosophila melanogaster_sentence_307

Using their hind legs, Drosophila proceed to groom their abdomen, and finally the wings and thorax. Drosophila melanogaster_sentence_308

Throughout this sequence, Drosophila periodically rub their legs together to get rid of excess dust and debris that accumulates during the grooming process. Drosophila melanogaster_sentence_309

Grooming behaviors have been shown to be executed in a suppression hierarchy. Drosophila melanogaster_sentence_310

This means that grooming behaviors that occur at the beginning of the sequence prevent those that come later in the sequence from occurring simultaneously, as the grooming sequence consists of mutually exclusive behaviors. Drosophila melanogaster_sentence_311

This hierarchy does not prevent Drosophila from returning to grooming behaviors that have already been accessed in the grooming sequence. Drosophila melanogaster_sentence_312

The order of grooming behaviors in the suppression hierarchy is thought to be related to the priority of cleaning a specific body part. Drosophila melanogaster_sentence_313

For example, the eyes and antennae are likely executed early on in the grooming sequence to prevent debris from interfering with the function of D. melanogaster’s sensory organs. Drosophila melanogaster_sentence_314

Walking Drosophila melanogaster_section_30

Like many other hexapod insects, Drosophila typically walk using a tripod gait. Drosophila melanogaster_sentence_315

This means that three of the legs swing together while the other three remain stationary, or in stance. Drosophila melanogaster_sentence_316

Variability around the tripod configuration appears to be continuous, meaning that flies do not exhibit distinct transitions between different gaits. Drosophila melanogaster_sentence_317

At fast walking speeds (15–30 mm/s), the walking configuration is mostly tripod (3 legs in stance), but at low walking speeds (0–15 mm/s), flies are more likely to have four or five legs in stance. Drosophila melanogaster_sentence_318

These transitions may help to optimize static stability. Drosophila melanogaster_sentence_319

Because flies are so small, inertial forces are negligible compared with the elastic forces of their muscles and joints or the viscous forces of the surrounding air. Drosophila melanogaster_sentence_320

In addition to stability, the robustness of a walking gait is also thought to be important in determining the gait of a fly at a particular walking speed. Drosophila melanogaster_sentence_321

Robustness refers to how much offset in the timing of a legs stance can be tolerated before the fly becomes statically unstable. Drosophila melanogaster_sentence_322

For instance, a robust gait may be particularly important when traversing uneven terrain, as it may cause unexpected disruptions in leg coordination. Drosophila melanogaster_sentence_323

Using a robust gait would help the fly maintain stability in this case. Drosophila melanogaster_sentence_324

Analyses suggest that Drosophila may exhibit a compromise between the most stable and most robust gait at a given walking speed. Drosophila melanogaster_sentence_325

Flight Drosophila melanogaster_section_31

Flies fly via straight sequences of movement interspersed by rapid turns called saccades. Drosophila melanogaster_sentence_326

During these turns, a fly is able to rotate 90° in less than 50 milliseconds. Drosophila melanogaster_sentence_327

Characteristics of Drosophila flight may be dominated by the viscosity of the air, rather than the inertia of the fly body, but the opposite case with inertia as the dominant force may occur. Drosophila melanogaster_sentence_328

However, subsequent work showed that while the viscous effects on the insect body during flight may be negligible, the aerodynamic forces on the wings themselves actually cause fruit flies' turns to be damped viscously. Drosophila melanogaster_sentence_329

Misconceptions Drosophila melanogaster_section_32

Drosophila is sometimes referred to as a pest due to its tendency to live in human settlements, where fermenting fruit is found. Drosophila melanogaster_sentence_330

Flies may collect in homes, restaurants, stores, and other locations. Drosophila melanogaster_sentence_331

However, because Drosophila do not transmit human disease and are essentially harmless, they do not fulfill the criteria to be classified as a pest. Drosophila melanogaster_sentence_332

The name and behavior of this species of fly has led to the misconception that it is a biological security risk in Australia. Drosophila melanogaster_sentence_333

While other "fruit fly" species do pose a risk, the D. melanogaster is attracted to fruit that is already rotting, rather than causing fruit to rot. Drosophila melanogaster_sentence_334

See also Drosophila melanogaster_section_33

Drosophila melanogaster_unordered_list_5


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Drosophila melanogaster.