Human Genome and Human Evolution

Summary

Summary. Each species has its own uniqueness, for which it is clear that species-specific genetic information forms the basis. The extent of genomic similarity among species can be evaluated by comparative studies of nucleotide substitutions in orthologous genes which are commonly present in all the species examined. Such studies using orthologous genes have shown that humans are most closely related to chimpanzees and that the nucleotide differences between them are merely a few percent. These studies are useful for construction of molecular phylogenetic trees and deduction of divergence dates, but are less useful for defining the genetic uniqueness of individual species. In order to elucidate the extent of dissimilarities among the genomes of humans and nonhuman primates and to clarify the genetic basis of human uniqueness, human-specific DNA sequences were sought as species-specific traits using the technique of genome subtraction. These sequences are present in the human genome alone but absent in the genomes of nonhuman primates.