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For a non-technical introduction to the topic, see Introduction to genetics. Genome_sentence_0

For other uses, see Genome (disambiguation). Genome_sentence_1

In the fields of molecular biology and genetics, a genome is all genetic material of an organism. Genome_sentence_2

It consists of DNA (or RNA in RNA viruses). Genome_sentence_3

The genome includes both the genes (the coding regions) and the noncoding DNA, as well as mitochondrial DNA and chloroplast DNA. Genome_sentence_4

The study of the genome is called genomics. Genome_sentence_5

Origin of term Genome_section_0

The term genome was created in 1920 by Hans Winkler, professor of botany at the University of Hamburg, Germany. Genome_sentence_6

The Oxford Dictionary suggests the name is a blend of the words gene and chromosome. Genome_sentence_7

However, see omics for a more thorough discussion. Genome_sentence_8

A few related -ome words already existed, such as biome and rhizome, forming a vocabulary into which genome fits systematically. Genome_sentence_9

Sequencing and mapping Genome_section_1

Further information: Genome project Genome_sentence_10

A genome sequence is the complete list of the nucleotides (A, C, G, and T for DNA genomes) that make up all the chromosomes of an individual or a species. Genome_sentence_11

Within a species, the vast majority of nucleotides are identical between individuals, but sequencing multiple individuals is necessary to understand the genetic diversity. Genome_sentence_12

In 1976, Walter Fiers at the University of Ghent (Belgium) was the first to establish the complete nucleotide sequence of a viral RNA-genome (Bacteriophage MS2). Genome_sentence_13

The next year, Fred Sanger completed the first DNA-genome sequence: Phage Φ-X174, of 5386 base pairs. Genome_sentence_14

The first complete genome sequences among all three domains of life were released within a short period during the mid-1990s: The first bacterial genome to be sequenced was that of Haemophilus influenzae, completed by a team at The Institute for Genomic Research in 1995. Genome_sentence_15

A few months later, the first eukaryotic genome was completed, with sequences of the 16 chromosomes of budding yeast Saccharomyces cerevisiae published as the result of a European-led effort begun in the mid-1980s. Genome_sentence_16

The first genome sequence for an archaeon, Methanococcus jannaschii, was completed in 1996, again by The Institute for Genomic Research. Genome_sentence_17

The development of new technologies has made genome sequencing dramatically cheaper and easier, and the number of complete genome sequences is growing rapidly. Genome_sentence_18

The US National Institutes of Health maintains one of several comprehensive databases of genomic information. Genome_sentence_19

Among the thousands of completed genome sequencing projects include those for rice, a mouse, the plant Arabidopsis thaliana, the puffer fish, and the bacteria E. Genome_sentence_20 coli. Genome_sentence_21

In December 2013, scientists first sequenced the entire genome of a Neanderthal, an extinct species of humans. Genome_sentence_22

The genome was extracted from the toe bone of a 130,000-year-old Neanderthal found in a Siberian cave. Genome_sentence_23

New sequencing technologies, such as massive parallel sequencing have also opened up the prospect of personal genome sequencing as a diagnostic tool, as pioneered by Manteia Predictive Medicine. Genome_sentence_24

A major step toward that goal was the completion in 2007 of the full genome of James D. Watson, one of the co-discoverers of the structure of DNA. Genome_sentence_25

Whereas a genome sequence lists the order of every DNA base in a genome, a genome map identifies the landmarks. Genome_sentence_26

A genome map is less detailed than a genome sequence and aids in navigating around the genome. Genome_sentence_27

The Human Genome Project was organized to map and to sequence the human genome. Genome_sentence_28

A fundamental step in the project was the release of a detailed genomic map by Jean Weissenbach and his team at the Genoscope in Paris. Genome_sentence_29

Reference genome sequences and maps continue to be updated, removing errors and clarifying regions of high allelic complexity. Genome_sentence_30

The decreasing cost of genomic mapping has permitted genealogical sites to offer it as a service, to the extent that one may submit one's genome to crowdsourced scientific endeavours such as DNA.LAND at the New York Genome Center, an example both of the economies of scale and of citizen science. Genome_sentence_31

Viral genomes Genome_section_2

Viral genomes can be composed of either RNA or DNA. Genome_sentence_32

The genomes of RNA viruses can be either single-stranded RNA or double-stranded RNA, and may contain one or more separate RNA molecules (segments: monopartit or multipartit genome). Genome_sentence_33

DNA viruses can have either single-stranded or double-stranded genomes. Genome_sentence_34

Most DNA virus genomes are composed of a single, linear molecule of DNA, but some are made up of a circular DNA molecule.There are also viral RNA called single stranded RNA: serves as template for mRNA synthesis and single stranded RNA: serves as template for DNA synthesis. Genome_sentence_35

Viral envelope is a outer layer of membrane that viral genomes use to enter the host cell. Genome_sentence_36

Some of the classes of viral DNA and RNA consists of a viral envelope while some do not. Genome_sentence_37


Class/ FamilyGenome_header_cell_0_0_0 Envelope?Genome_header_cell_0_0_1
Double-stranded DNAGenome_cell_0_1_0 Genome_cell_0_1_1
AdenovirusGenome_cell_0_2_0 NoGenome_cell_0_2_1
PapillomavirusGenome_cell_0_3_0 NoGenome_cell_0_3_1
PolyomavirusGenome_cell_0_4_0 NoGenome_cell_0_4_1
HerpesvirusGenome_cell_0_5_0 YesGenome_cell_0_5_1
PoxvirusGenome_cell_0_6_0 YesGenome_cell_0_6_1
Single-stranded DNAGenome_cell_0_7_0 Genome_cell_0_7_1
ParvovirusGenome_cell_0_8_0 NoGenome_cell_0_8_1
Double-stranded RNAGenome_cell_0_9_0 Genome_cell_0_9_1
ReovirusGenome_cell_0_10_0 NoGenome_cell_0_10_1
Single-stranded RNAGenome_cell_0_11_0 Genome_cell_0_11_1
PicornavirusGenome_cell_0_12_0 NoGenome_cell_0_12_1
CoronavirusGenome_cell_0_13_0 YesGenome_cell_0_13_1
FlavivirusGenome_cell_0_14_0 YesGenome_cell_0_14_1
TogavirusGenome_cell_0_15_0 YesGenome_cell_0_15_1
Single-stranded RNA: Serves as template for mRNA synthesisGenome_cell_0_16_0 Genome_cell_0_16_1
FilovirusGenome_cell_0_17_0 YesGenome_cell_0_17_1
OrthomyxovirusGenome_cell_0_18_0 YesGenome_cell_0_18_1
ParamyxovirusGenome_cell_0_19_0 YesGenome_cell_0_19_1
RhabdovirusGenome_cell_0_20_0 YesGenome_cell_0_20_1
Single-stranded RNA: serves as template for DNA synthesisGenome_cell_0_21_0 Genome_cell_0_21_1
RetrovirusGenome_cell_0_22_0 YesGenome_cell_0_22_1

Prokaryotic genomes Genome_section_3

Prokaryotes and eukaryotes have DNA genomes. Genome_sentence_38

Archaea and most bacteria have a single circular chromosome, however, some bacterial species have linear or multiple chromosomes. Genome_sentence_39

If the DNA is replicated faster than the bacterial cells divide, multiple copies of the chromosome can be present in a single cell, and if the cells divide faster than the DNA can be replicated, multiple replication of the chromosome is initiated before the division occurs, allowing daughter cells to inherit complete genomes and already partially replicated chromosomes. Genome_sentence_40

Most prokaryotes have very little repetitive DNA in their genomes. Genome_sentence_41

However, some symbiotic bacteria (e.g. Serratia symbiotica) have reduced genomes and a high fraction of pseudogenes: only ~40% of their DNA encodes proteins. Genome_sentence_42

Some bacteria have auxiliary genetic material, also part of their genome, which is carried in plasmids. Genome_sentence_43

For this, the word genome should not be used as a synonym of chromosome. Genome_sentence_44

Eukaryotic genomes Genome_section_4

See also: Eukaryotic chromosome fine structure Genome_sentence_45

Eukaryotic genomes are composed of one or more linear DNA chromosomes. Genome_sentence_46

The number of chromosomes varies widely from Jack jumper ants and an asexual nemotode, which each have only one pair, to a fern species that has 720 pairs. Genome_sentence_47

A typical human cell has two copies of each of 22 autosomes, one inherited from each parent, plus two sex chromosomes, making it diploid. Genome_sentence_48

Gametes, such as ova, sperm, spores, and pollen, are haploid, meaning they carry only one copy of each chromosome. Genome_sentence_49

In addition to the chromosomes in the nucleus, organelles such as the chloroplasts and mitochondria have their own DNA. Genome_sentence_50

Mitochondria are sometimes said to have their own genome often referred to as the "mitochondrial genome". Genome_sentence_51

The DNA found within the chloroplast may be referred to as the "plastome". Genome_sentence_52

Like the bacteria they originated from, mitochondria and chloroplasts have a circular chromosome. Genome_sentence_53

Unlike prokaryotes, eukaryotes have exon-intron organization of protein coding genes and variable amounts of repetitive DNA. Genome_sentence_54

In mammals and plants, the majority of the genome is composed of repetitive DNA. Genome_sentence_55

Coding sequences Genome_section_5

DNA sequences that carry the instructions to make proteins are referred to as coding sequences. Genome_sentence_56

The proportion of the genome occupied by coding sequences varies widely. Genome_sentence_57

A larger genome does not necessarily contain more genes, and the proportion of non-repetitive DNA decreases along with increasing genome size in complex eukaryotes. Genome_sentence_58

Noncoding sequences Genome_section_6

Main article: Non-coding DNA Genome_sentence_59

See also: Intergenic region Genome_sentence_60

Noncoding sequences include introns, sequences for non-coding RNAs, regulatory regions, and repetitive DNA. Genome_sentence_61

Noncoding sequences make up 98% of the human genome. Genome_sentence_62

There are two categories of repetitive DNA in the genome: tandem repeats and interspersed repeats. Genome_sentence_63

Tandem repeats Genome_section_7

Short, non-coding sequences that are repeated head-to-tail are called tandem repeats. Genome_sentence_64

Microsatellites consisting of 2-5 basepair repeats, while minisatellite repeats are 30-35 bp. Genome_sentence_65

Tandem repeats make up about 4% of the human genome and 9% of the fruit fly genome. Genome_sentence_66

Tandem repeats can be functional. Genome_sentence_67

For example, telomeres are composed of the tandem repeat TTAGGG in mammals, and they play an important role in protecting the ends of the chromosome. Genome_sentence_68

In other cases, expansions in the number of tandem repeats in exons or introns can cause disease. Genome_sentence_69

For example, the human gene huntingtin typically contains 6–29 tandem repeats of the nucleotides CAG (encoding a polyglutamine tract). Genome_sentence_70

An expansion to over 36 repeats results in Huntington's disease, a neurodegenerative disease. Genome_sentence_71

Twenty human disorders are known to result from similar tandem repeat expansions in various genes. Genome_sentence_72

The mechanism by which proteins with expanded polygulatamine tracts cause death of neurons is not fully understood. Genome_sentence_73

One possibility is that the proteins fail to fold properly and avoid degradation, instead accumulating in aggregates that also sequester important transcription factors, thereby altering gene expression. Genome_sentence_74

Tandem repeats are usually caused by slippage during replication, unequal crossing-over and gene conversion. Genome_sentence_75

Transposable elements Genome_section_8

Transposable elements (TEs) are sequences of DNA with a defined structure that are able to change their location in the genome. Genome_sentence_76

TEs are categorized as either class I TEs, which replicate by a copy-and-paste mechanism, or class II TEs, which can be excised from the genome and inserted at a new location. Genome_sentence_77

The movement of TEs is a driving force of genome evolution in eukaryotes because their insertion can disrupt gene functions, homologous recombination between TEs can produce duplications, and TE can shuffle exons and regulatory sequences to new locations. Genome_sentence_78

Retrotransposons Genome_section_9

Retrotransposons are found mostly in eukaryotes but not found in prokaryotes and retrotransposons form a large portion of genomes of many eukaryotes. Genome_sentence_79

Retrotransposon is a transposable element that transpose through an RNA intermediate. Genome_sentence_80

Retrotransposons are composed of DNA, but are transcribed into RNA for transposition, then the RNA transcript is copied back to DNA formation with the help of a specific enzyme called reverse transcriptase. Genome_sentence_81

Retrotransposons that carry reverse transcriptase in their gene can trigger its own transposition but the genes that lack the reverse transcriptase must use reverse transcriptase synthesized by another retrotransposon. Genome_sentence_82

Retrotransposons can be transcribed into RNA, which are then duplicated at another site into the genome. Genome_sentence_83

Retrotransposons can be divided into long terminal repeats (LTRs) and non-long terminal repeats (Non-LTRs). Genome_sentence_84

Long terminal repeats (LTRs) are derived from ancient retroviral infections, so they encode proteins related to retroviral proteins including gag (structural proteins of the virus), pol (reverse transcriptase and integrase), pro (protease), and in some cases env (envelope) genes. Genome_sentence_85

These genes are flanked by long repeats at both 5' and 3' ends. Genome_sentence_86

It has been reported that LTRs consist of the largest fraction in most plant genome and might account for the huge variation in genome size. Genome_sentence_87

Non-long terminal repeats (Non-LTRs) are classified as long interspersed nuclear elements (LINEs), short interspersed nuclear elements (SINEs), and Penelope-like elements (PLEs). Genome_sentence_88

In Dictyostelium discoideum, there is another DIRS-like elements belong to Non-LTRs. Genome_sentence_89

Non-LTRs are widely spread in eukaryotic genomes. Genome_sentence_90

Long interspersed elements (LINEs) encode genes for reverse transcriptase and endonuclease, making them autonomous transposable elements. Genome_sentence_91

The human genome has around 500,000 LINEs, taking around 17% of the genome. Genome_sentence_92

Short interspersed elements (SINEs) are usually less than 500 base pairs and are non-autonomous, so they rely on the proteins encoded by LINEs for transposition. Genome_sentence_93

The Alu element is the most common SINE found in primates. Genome_sentence_94

It is about 350 base pairs and occupies about 11% of the human genome with around 1,500,000 copies. Genome_sentence_95

DNA transposons Genome_section_10

DNA transposons encode a transposase enzyme between inverted terminal repeats. Genome_sentence_96

When expressed, the transposase recognizes the terminal inverted repeats that flank the transposon and catalyzes its excision and reinsertion in a new site. Genome_sentence_97

This cut-and-paste mechanism typically reinserts transposons near their original location (within 100kb). Genome_sentence_98

DNA transposons are found in bacteria and make up 3% of the human genome and 12% of the genome of the roundworm C. Genome_sentence_99 elegans. Genome_sentence_100

Genome size Genome_section_11

Genome size is the total number of DNA base pairs in one copy of a haploid genome. Genome_sentence_101

Genome size varies widely across species. Genome_sentence_102

In humans, the nuclear genome comprises approximately 3.2 billion nucleotides of DNA, divided into 24 linear molecules, the shortest 50 000 000 nucleotides in length and the longest 260 000 000 nucleotides, each contained in a different chromosome. Genome_sentence_103

There is no clear and consistent correlation between morphological complexity and genome size in either prokaryotes or lower eukaryotes. Genome_sentence_104

Genome size is largely a function of the expansion and contraction of repetitive DNA elements. Genome_sentence_105

Since genomes are very complex, one research strategy is to reduce the number of genes in a genome to the bare minimum and still have the organism in question survive. Genome_sentence_106

There is experimental work being done on minimal genomes for single cell organisms as well as minimal genomes for multi-cellular organisms (see Developmental biology). Genome_sentence_107

The work is both in vivo and in silico. Genome_sentence_108

Here is a table of some significant or representative genomes. Genome_sentence_109

See #See also for lists of sequenced genomes. Genome_sentence_110


Organism typeGenome_header_cell_1_0_0 OrganismGenome_header_cell_1_0_1 Genome size

(base pairs)Genome_header_cell_1_0_2

Approx. no. of genesGenome_header_cell_1_0_4 NoteGenome_header_cell_1_0_5
VirusGenome_cell_1_1_0 Porcine circovirus type 1Genome_cell_1_1_1 1,759Genome_cell_1_1_2 1.8kbGenome_cell_1_1_3 Genome_cell_1_1_4 Smallest viruses replicating autonomously in eukaryotic cells.Genome_cell_1_1_5
VirusGenome_cell_1_2_0 Bacteriophage MS2Genome_cell_1_2_1 3,569Genome_cell_1_2_2 3.5kbGenome_cell_1_2_3 Genome_cell_1_2_4 First sequenced RNA-genomeGenome_cell_1_2_5
VirusGenome_cell_1_3_0 SV40Genome_cell_1_3_1 5,224Genome_cell_1_3_2 5.2kbGenome_cell_1_3_3 Genome_cell_1_3_4 Genome_cell_1_3_5
VirusGenome_cell_1_4_0 Phage Φ-X174Genome_cell_1_4_1 5,386Genome_cell_1_4_2 5.4kbGenome_cell_1_4_3 Genome_cell_1_4_4 First sequenced DNA-genomeGenome_cell_1_4_5
VirusGenome_cell_1_5_0 HIVGenome_cell_1_5_1 9,749Genome_cell_1_5_2 9.7kbGenome_cell_1_5_3 Genome_cell_1_5_4 Genome_cell_1_5_5
VirusGenome_cell_1_6_0 Phage λGenome_cell_1_6_1 48,502Genome_cell_1_6_2 48.5kbGenome_cell_1_6_3 Genome_cell_1_6_4 Often used as a vector for the cloning of recombinant DNA.Genome_cell_1_6_5
VirusGenome_cell_1_7_0 MegavirusGenome_cell_1_7_1 1,259,197Genome_cell_1_7_2 1.3MbGenome_cell_1_7_3 Genome_cell_1_7_4 Until 2013 the largest known viral genome.Genome_cell_1_7_5
VirusGenome_cell_1_8_0 Pandoravirus salinusGenome_cell_1_8_1 2,470,000Genome_cell_1_8_2 2.47MbGenome_cell_1_8_3 Genome_cell_1_8_4 Largest known viral genome.Genome_cell_1_8_5
Eukaryotic organelleGenome_cell_1_9_0 Human mitochondrionGenome_cell_1_9_1 16,569Genome_cell_1_9_2 16.6kbGenome_cell_1_9_3 Genome_cell_1_9_4 Genome_cell_1_9_5
BacteriumGenome_cell_1_10_0 Nasuia deltocephalinicola (strain NAS-ALF)Genome_cell_1_10_1 112,091Genome_cell_1_10_2 112kbGenome_cell_1_10_3 137Genome_cell_1_10_4 Smallest known non-viral genome. Symbiont of leafhoppers.Genome_cell_1_10_5
BacteriumGenome_cell_1_11_0 Carsonella ruddiiGenome_cell_1_11_1 159,662Genome_cell_1_11_2 160kbGenome_cell_1_11_3 Genome_cell_1_11_4 An endosymbiont of psyllid insectsGenome_cell_1_11_5
BacteriumGenome_cell_1_12_0 Buchnera aphidicolaGenome_cell_1_12_1 600,000Genome_cell_1_12_2 600kbGenome_cell_1_12_3 Genome_cell_1_12_4 An endosymbiont of aphidsGenome_cell_1_12_5
BacteriumGenome_cell_1_13_0 Wigglesworthia glossinidiaGenome_cell_1_13_1 700,000Genome_cell_1_13_2 700KbGenome_cell_1_13_3 Genome_cell_1_13_4 A symbiont in the gut of the tsetse flyGenome_cell_1_13_5
BacteriumcyanobacteriumGenome_cell_1_14_0 Prochlorococcus spp. (1.7 Mb)Genome_cell_1_14_1 1,700,000Genome_cell_1_14_2 1.7MbGenome_cell_1_14_3 1,884Genome_cell_1_14_4 Smallest known cyanobacterium genome. One of the primary photosynthesizers on Earth.Genome_cell_1_14_5
BacteriumGenome_cell_1_15_0 Haemophilus influenzaeGenome_cell_1_15_1 1,830,000Genome_cell_1_15_2 1.8MbGenome_cell_1_15_3 Genome_cell_1_15_4 First genome of a living organism sequenced, July 1995Genome_cell_1_15_5
BacteriumGenome_cell_1_16_0 Escherichia coliGenome_cell_1_16_1 4,600,000Genome_cell_1_16_2 4.6MbGenome_cell_1_16_3 4,288Genome_cell_1_16_4 Genome_cell_1_16_5
Bacterium – cyanobacteriumGenome_cell_1_17_0 Nostoc punctiformeGenome_cell_1_17_1 9,000,000Genome_cell_1_17_2 9MbGenome_cell_1_17_3 7,432Genome_cell_1_17_4 7432 open reading framesGenome_cell_1_17_5
BacteriumGenome_cell_1_18_0 Solibacter usitatus (strain Ellin 6076)Genome_cell_1_18_1 9,970,000Genome_cell_1_18_2 10MbGenome_cell_1_18_3 Genome_cell_1_18_4 Genome_cell_1_18_5
AmoeboidGenome_cell_1_19_0 Polychaos dubium ("Amoeba" dubia)Genome_cell_1_19_1 670,000,000,000Genome_cell_1_19_2 670GbGenome_cell_1_19_3 Genome_cell_1_19_4 Largest known genome. (Disputed)Genome_cell_1_19_5
PlantGenome_cell_1_20_0 Genlisea tuberosaGenome_cell_1_20_1 61,000,000Genome_cell_1_20_2 61MbGenome_cell_1_20_3 Genome_cell_1_20_4 Smallest recorded flowering plant genome, 2014.Genome_cell_1_20_5
PlantGenome_cell_1_21_0 Arabidopsis thalianaGenome_cell_1_21_1 135,000,000Genome_cell_1_21_2 135 MbGenome_cell_1_21_3 27,655Genome_cell_1_21_4 First plant genome sequenced, December 2000.Genome_cell_1_21_5
PlantGenome_cell_1_22_0 Populus trichocarpaGenome_cell_1_22_1 480,000,000Genome_cell_1_22_2 480MbGenome_cell_1_22_3 73,013Genome_cell_1_22_4 First tree genome sequenced, September 2006Genome_cell_1_22_5
PlantGenome_cell_1_23_0 Fritillaria assyriacaGenome_cell_1_23_1 130,000,000,000Genome_cell_1_23_2 130GbGenome_cell_1_23_3 Genome_cell_1_23_4 Genome_cell_1_23_5
PlantGenome_cell_1_24_0 Paris japonica (Japanese-native, pale-petal)Genome_cell_1_24_1 150,000,000,000Genome_cell_1_24_2 150GbGenome_cell_1_24_3 Genome_cell_1_24_4 Largest plant genome knownGenome_cell_1_24_5
PlantmossGenome_cell_1_25_0 Physcomitrella patensGenome_cell_1_25_1 480,000,000Genome_cell_1_25_2 480MbGenome_cell_1_25_3 Genome_cell_1_25_4 First genome of a bryophyte sequenced, January 2008.Genome_cell_1_25_5
FungusyeastGenome_cell_1_26_0 Saccharomyces cerevisiaeGenome_cell_1_26_1 12,100,000Genome_cell_1_26_2 12.1MbGenome_cell_1_26_3 6,294Genome_cell_1_26_4 First eukaryotic genome sequenced, 1996Genome_cell_1_26_5
FungusGenome_cell_1_27_0 Aspergillus nidulansGenome_cell_1_27_1 30,000,000Genome_cell_1_27_2 30MbGenome_cell_1_27_3 9,541Genome_cell_1_27_4 Genome_cell_1_27_5
NematodeGenome_cell_1_28_0 Pratylenchus coffeaeGenome_cell_1_28_1 20,000,000Genome_cell_1_28_2 20MbGenome_cell_1_28_3 Genome_cell_1_28_4 Smallest animal genome knownGenome_cell_1_28_5
NematodeGenome_cell_1_29_0 Caenorhabditis elegansGenome_cell_1_29_1 100,300,000Genome_cell_1_29_2 100MbGenome_cell_1_29_3 19,000Genome_cell_1_29_4 First multicellular animal genome sequenced, December 1998Genome_cell_1_29_5
InsectGenome_cell_1_30_0 Drosophila melanogaster (fruit fly)Genome_cell_1_30_1 175,000,000Genome_cell_1_30_2 175MbGenome_cell_1_30_3 13,600Genome_cell_1_30_4 Size variation based on strain (175-180Mb; standard y w strain is 175Mb)Genome_cell_1_30_5
InsectGenome_cell_1_31_0 Apis mellifera (honey bee)Genome_cell_1_31_1 236,000,000Genome_cell_1_31_2 236MbGenome_cell_1_31_3 10,157Genome_cell_1_31_4 Genome_cell_1_31_5
InsectGenome_cell_1_32_0 Bombyx mori (silk moth)Genome_cell_1_32_1 432,000,000Genome_cell_1_32_2 432MbGenome_cell_1_32_3 14,623Genome_cell_1_32_4 14,623 predicted genesGenome_cell_1_32_5
InsectGenome_cell_1_33_0 Solenopsis invicta (fire ant)Genome_cell_1_33_1 480,000,000Genome_cell_1_33_2 480MbGenome_cell_1_33_3 16,569Genome_cell_1_33_4 Genome_cell_1_33_5
MammalGenome_cell_1_34_0 Mus musculusGenome_cell_1_34_1 2,700,000,000Genome_cell_1_34_2 2.7GbGenome_cell_1_34_3 20,210Genome_cell_1_34_4 Genome_cell_1_34_5
MammalGenome_cell_1_35_0 Pan paniscusGenome_cell_1_35_1 3,286,640,000Genome_cell_1_35_2 3.3GbGenome_cell_1_35_3 20,000Genome_cell_1_35_4 Bonobo - estimated genome size 3.29 billion bpGenome_cell_1_35_5
MammalGenome_cell_1_36_0 Homo sapiensGenome_cell_1_36_1 3,000,000,000Genome_cell_1_36_2 3GbGenome_cell_1_36_3 20,000Genome_cell_1_36_4 Homo sapiens genome size estimated at 3.2 Gbp in 2001

Initial sequencing and analysis of the human genomeGenome_cell_1_36_5

BirdGenome_cell_1_37_0 Gallus gallusGenome_cell_1_37_1 1,043,000,000Genome_cell_1_37_2 1.0GbGenome_cell_1_37_3 20,000Genome_cell_1_37_4 Genome_cell_1_37_5
FishGenome_cell_1_38_0 Tetraodon nigroviridis (type of puffer fish)Genome_cell_1_38_1 385,000,000Genome_cell_1_38_2 390MbGenome_cell_1_38_3 Genome_cell_1_38_4 Smallest vertebrate genome known estimated to be 340 Mb – 385 Mb.Genome_cell_1_38_5
FishGenome_cell_1_39_0 Protopterus aethiopicus (marbled lungfish)Genome_cell_1_39_1 130,000,000,000Genome_cell_1_39_2 130GbGenome_cell_1_39_3 Genome_cell_1_39_4 Largest vertebrate genome knownGenome_cell_1_39_5

Genomic alterations Genome_section_12

All the cells of an organism originate from a single cell, so they are expected to have identical genomes; however, in some cases, differences arise. Genome_sentence_111

Both the process of copying DNA during cell division and exposure to environmental mutagens can result in mutations in somatic cells. Genome_sentence_112

In some cases, such mutations lead to cancer because they cause cells to divide more quickly and invade surrounding tissues. Genome_sentence_113

In certain lymphocytes in the human immune system, V(D)J recombination generates different genomic sequences such that each cell produces a unique antibody or T cell receptors. Genome_sentence_114

During meiosis, diploid cells divide twice to produce haploid germ cells. Genome_sentence_115

During this process, recombination results in a reshuffling of the genetic material from homologous chromosomes so each gamete has a unique genome. Genome_sentence_116

Genome-wide reprogramming Genome_section_13

Genome-wide reprogramming in mouse primordial germ cells involves epigenetic imprint erasure leading to totipotency. Genome_sentence_117

Reprogramming is facilitated by active DNA demethylation, a process that entails the DNA base excision repair pathway. Genome_sentence_118

This pathway is employed in the erasure of CpG methylation (5mC) in primordial germ cells. Genome_sentence_119

The erasure of 5mC occurs via its conversion to 5-hydroxymethylcytosine (5hmC) driven by high levels of the ten-eleven dioxygenase enzymes TET1 and TET2. Genome_sentence_120

Genome evolution Genome_section_14

Genomes are more than the sum of an organism's genes and have traits that may be measured and studied without reference to the details of any particular genes and their products. Genome_sentence_121

Researchers compare traits such as karyotype (chromosome number), genome size, gene order, codon usage bias, and GC-content to determine what mechanisms could have produced the great variety of genomes that exist today (for recent overviews, see Brown 2002; Saccone and Pesole 2003; Benfey and Protopapas 2004; Gibson and Muse 2004; Reese 2004; Gregory 2005). Genome_sentence_122

Duplications play a major role in shaping the genome. Genome_sentence_123

Duplication may range from extension of short tandem repeats, to duplication of a cluster of genes, and all the way to duplication of entire chromosomes or even entire genomes. Genome_sentence_124

Such duplications are probably fundamental to the creation of genetic novelty. Genome_sentence_125

Horizontal gene transfer is invoked to explain how there is often an extreme similarity between small portions of the genomes of two organisms that are otherwise very distantly related. Genome_sentence_126

Horizontal gene transfer seems to be common among many microbes. Genome_sentence_127

Also, eukaryotic cells seem to have experienced a transfer of some genetic material from their chloroplast and mitochondrial genomes to their nuclear chromosomes. Genome_sentence_128

Recent empirical data suggest an important role of viruses and sub-viral RNA-networks to represent a main driving role to generate genetic novelty and natural genome editing. Genome_sentence_129

In fiction Genome_section_15

Works of science fiction illustrate concerns about the availability of genome sequences. Genome_sentence_130

Michael Crichton's 1990 novel Jurassic Park and the subsequent film tell the story of a billionaire who creates a theme park of cloned dinosaurs on a remote island, with disastrous outcomes. Genome_sentence_131

A geneticist extracts dinosaur DNA from the blood of ancient mosquitoes and fills in the gaps with DNA from modern species to create several species of dinosaurs. Genome_sentence_132

A chaos theorist is asked to give his expert opinion on the safety of engineering an ecosystem with the dinosaurs, and he repeatedly warns that the outcomes of the project will be unpredictable and ultimately uncontrollable. Genome_sentence_133

These warnings about the perils of using genomic information are a major theme of the book. Genome_sentence_134

The 1997 film Gattaca is set in a futurist society where genomes of children are engineered to contain the most ideal combination of their parents' traits, and metrics such as risk of heart disease and predicted life expectancy are documented for each person based on their genome. Genome_sentence_135

People conceived outside of the eugenics program, known as "In-Valids" suffer discrimination and are relegated to menial occupations. Genome_sentence_136

The protagonist of the film is an In-Valid who works to defy the supposed genetic odds and achieve his dream of working as a space navigator. Genome_sentence_137

The film warns against a future where genomic information fuels prejudice and extreme class differences between those who can and can't afford genetically engineered children. Genome_sentence_138

See also Genome_section_16

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