5.11: The Human and Chimpanzee Genomes

Comparison results

Their genomes are 98.8% identical (between any two humans — picked at random — the figure is closer to 99.5%).

• Another gene product that differs between the two species is the protein FoxP2. FoxP2 is a transcription factor. Rare humans with only one copy of the gene (FOXP2) have severe language defects.

  The human FOXP2 gene differs from that of the chimp by 5 nucleotides, 2 of which result in non-synonymous codons encoding 2 different amino acids in the protein. The human protein differs from that in the mouse by only 3 amino acids. When you consider that we shared a common ancestor with mice over 60 million years ago but with the champanzee only about 6 million years ago, it is tempting to think that these recent changes in the human gene are related to the acquisition of language.

• While there are only small (~1%) coding differences in their genes, their genomes differ in other ways.
  • Many insertions and deletions ("indels") and
  • many gene duplications
  are found in one species but not the other. Later work has revealed that of 510 chimpanzee sequences that are deleted in the human genome, only one occurs in the coding region of a gene. The others are found in introns or between genes, and at least some of these occur in gene-regulatory regions like enhancers.
• Many single-nucleotide differences create different splicing sites so alternative splicing can produce substantial differences in the proteins of two species.