|Sizing up genomes: Amoeba is king|
|Reasons for the size of a genome and the number of genes are not clear|
Edward R. Winstead
February 12, 2001
Biologists have been estimating the size of genomes for decades. In 1971, for example, researchers reported that a species of Italian bat, Miniopterus, has a genome half the size of the human genome. Similarly, the genome of Muntiacus, a species of Asian barking deer, was estimated at about 70 percent of that of humans. As reported this week, the human genome contains about 3 billion chemical units of DNA, or base pairs.
In the animal kingdom, the relationship between genome size and evolutionary status is not clear. One of the largest genomes belongs to a very small creature, Amoeba dubia. This protozoan genome has 670 billion units of DNA, or base pairs. The genome of a cousin, Amoeba proteus, has a mere 290 billion base pairs, making it 100 times larger than the human genome.
A Sample of Species and Genome Size (in base pairs)
Among the organisms whose genomes are sequenced, genome size does not correlate with the number of genes.
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