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August 2003 Issue

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Evidence of Shared Heritage Between Humans and Primates

Published August 2003

Li Jin, PhD, professor of environmental health at the UC College of Medicine, and his colleagues from the Chinese Human Genome Center at Shanghai and Fudan University recently confirmed in a continuing study that chimpanzees are our closest genetic relatives. By sequencing the coding and regulatory regions of 127 known genes on human chromosome 21 in DNA samples from humans and chimpanzees, the researchers compared the differences. Their findings support the presence of natural selection in the evolution of the human genome. The study also revealed that the relative evolution span between humans and chimpanzees is 4.93 million years.

Using DNA samples from humans, chimpanzees, gorillas, orangutans, and macaques allowed for a direct comparison among the species. In the last 20 years, DNA sequencing has strengthened the notion that despite their phenotypic differences, the genomes of humans and primates are strikingly similar.

"By implementing a bioinformatics based approach, we show that the identification of genetic variants specific to the human lineage might lead to an understanding of the mechanisms that are attributable to the phenotypes that are unique to humans, by changing the structure and/or dosage of the proteins expressed," said Dr. Jin.

The comparison between humans and chimpanzees yielded that the difference in the coding and regulatory regions is significantly lower than that observed in random genomic regions, which suggests the presence of natural selection in the human genome. Another benefit of the study is that by sequencing human chromosome 21, the smallest chromosome in the human genome, a better understanding of regions corresponding to mental retardation may emerge.

Other revelations have included that some primates, such as chimpanzees and bonobos share nearly 99 percent of human sequences. This has led some scientists to argue that knowing the complete genome of at least one of these species will aid in identifying the genes that contribute to what makes us human.

The study, which began two years ago, started as a collaborative project between the Chinese Human Genome Center at Shanghai, Fudan University and the Center for Genome Information (CGI) at UC. More progress in areas such as characterization of genetic structure of world populations, origin and pre-historical migrations of human populations in East Asia and Southeast Asia is expected.

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