genome

Full complement of genes carried by a single (haploid) set of chromosomes. The term may be applied to the genetic information carried by an individual or to the range of genes found in a given species.

The human genome is made up of around 3 billion basepairs, most of which were reported in draft genome sequences obtained in 2003 by the Human Genome Project and by a commercial sequencing initiative. Complete and final sequences for individual chromosomes have been reported since then, but the total number of human genes, now estimated to be close to 30,000, remains uncertain.

The first genomes of cellular organisms to be sequenced in full were those of the bacteria Haemofilus influenzae and Mycoplasma genitalium, in 1995. Methanococcus jannaschii was the first archaeon to be sequenced in full, in 1996, and the baker's yeast Saccharomyces cerevisiae the first eukaryote, in 1997. Dozens of other microbial genome sequences followed during the second half of the 1990s.

Landmark genome sequences of higher organisms included fruit fly (2000), mouse (2002), dog (2003), rat (2004), bee (2004), and chimpanzee (2005). The latter has proven a particularly useful reference for the study of human evolution, and as a reference point for the investigation of human population genetics.

Animal species can have drastically different sized genomes even when the species are roughly the same size. In 2000, UK researchers in Scotland noted a correlation between bird genome size and lifespan, finding that birds with larger genomes lived for longer.