Genome facts for kids

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UCSC human chromosome colours
An image of the 46 chromosomes making up the diploid genome of a human male. (The mitochondrial chromosome is not shown.)

The genome of an organism is the whole of its hereditary information encoded in its DNA (or, for some viruses, RNA). This includes both the genes and the non-coding sequences of the DNA. The term was coined in 1920.

Winkler's definition, in translation, runs:

"I propose the expression genome for the haploid chromosome set, which, together with the pertinent protoplasm, specifies the material foundations of the species ...." p165

However, no single haploid chromosome set defines even the DNA of a species, because of the huge variety of alleles carried by a population. Even a diploid individual carries genetic variety. For that reason Dobzhansky preferred "set of chromosomes", and the definition now must be broader than Winklers' definition. The genome of a haploid chromosome set is merely a sample of the total genetic variety of a species.

The term 'genome' can be applied specifically to mean the complete set of nuclear DNA (the 'nuclear genome') but can also be used of organelles that contain their own DNA, as with the mitochondrial genome or the chloroplast genome.

Genome sizes

Organism Genome size (base pairs) Note
Virus, Bacteriophage MS2 3569 First sequenced RNA-genome
Virus, SV40 5224
Virus, Phage Φ-X174 5386 First sequenced DNA-genome
Virus, Phage λ 5×104
Bacterium, Candidatus Carsonella ruddii 1.6×105 Smallest non-viral genome, Feb 2007
Bacterium, Escherichia coli 4×106 Best-researched bacterium.
Bacterium, Solibactoer usitatus 1×107 Largest known bacterial genome
Protist, Amoeba dubia 6.7×1011 Largest known genome, but disputed.
Plant, Arabidopsis thaliana 1.57×108 First plant genome sequenced, Dec 2000.
Plant, Genlisea margaretae 6.34×107 Smallest recorded flowering plant genome, 2006.
Plant, Fritillaria assyrica 1.3×1011
Plant, Populus trichocarpa 4.8×108 First tree genome, Sept 2006
Yeast, Saccharomyces cerevisiae 2×107
Fungus, Aspergillus nidulans 3×107
Nematode, Caenorhabditis elegans 9.8×107 First multicellular animal genome, December 1998.
Insect, Drosophila melanogaster aka fruit fly 1.3×108
Insect, Bombyx mori aka silk moth 5.30×108
Insect, Apis mellifera aka honey bee 1.77×109
Fish, Tetraodon nigroviridis, type of Puffer fish 3.85×108 Smallest vertebrate genome known
Mammal, Homo sapiens 3×109
Fish, Protopterus aethiopicus aka marbled lungfish 1.3×1011 Largest vertebrate genome known

Note: The DNA from a single human cell has a length of ~1.8 m (but at a width of ~2.4 nanometers).

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Genome Facts for Kids. Kiddle Encyclopedia.