Genome

A genome is all the hereditary information held by an organism, this includes both expressed and non-expressed genetic information. It is usually stored in DNA though the Retrovirus stores it in RNA.

Eukaryotes (including humans) actually have two types of genomic material:

1. chromosonal material: Information found inside the nucleus of a cell
2. mitochondrial material: Information found inside a cytoplasm of a cell, specifically in the mitochondria (this separate genome is used as evidence for the Endosymbiotic hypothesis).

The Human Genome Project mapped the genome of humans (Homo sapiens) in a 13-year study, and is considered one of the marvels of modern human medicine and biology. All of the information is stored in a database. It is expected that the results of the project will allow scientists to predict how genetics influences drug interaction with the body, and lead to target specific drugs.

Genomes of other species have been recorded as well, such as mice, chimpanzees and yeast. The mouse genome sequence from the C57BL/6J strain has about 30,000 genes, and 99% of them have direct counterparts in humans.

The chimpanzee represented the first non-human primate sequenced. The differences in the chimpanzee and human genomes are small, with 99% of the DNA sequence preserved. The differences can be classified in terms of differences in local single nucleotide substitutions, insertions, deletions and repetitions of sequences. A relatively large number of difference between the chimpanzee and human genomes are not due to substitutions. When this is taken into account, humans and chimpanzees still share 96% of their sequence, and are genetically closer than rats and mice.