Chimpanzee genes show what it means to be human
By Roger Highfield, Science Editor
(Filed: 01/09/2005) Scientists have pieced together the genetic recipe of the chimpanzee, marking a milestone in the centuries-old quest to discover what sets humans apart from other animals. Although humans did not evolve from chimps - they shared an apelike ancestor some six million years ago - they are our closest living relative. Differences in the sequence of four chemical "letters" that spell out the genetic codes, or genomes, of chimp (Pan troglodytes) and man (Homo sapiens) could account for the very human abilities to write opera, build cathedrals and walk on the Moon. The comparisons of the two genomes, published today in the journal Nature by 67 researchers in the Chimpanzee Sequencing and Analysis Consortium, provide unambiguous confirmation of the common and recent evolutionary origin of humans and chimpanzees, as first predicted by Charles Darwin in 1871. But they suggest that our species may be more different from the great apes than previously thought: the differences between the chimp and human genomes is 10 times greater than that which occurs between any two humans, but 10 times less than the differences between the mouse and rat. Today's studies contain good news for men: contrary to some dire predictions made recently, the Y chromosome that distinguishes men from women is not heading for extinction, unlike the chimp Y which appears to be endangered by the ape's more promiscuous lifestyle, according to a report by Dr David Page, Dr Jennifer Hughes and colleagues at the Whitehead Institute, near Boston. Both male and female chimps engage with multiple partners when they mate, placing less pressure on evolution to preserve those genes on the Y whose functions have nothing to do with reproduction. Because humans historically have been largely monogamous, our Y chromosomes have been spared. To obtain the chimp genome, scientists analysed cells grown from Clint, at Emory University's Yerkes National Primate Research Centre. Clint spent his whole life at the facility and died last year of heart failure at 24. A refined version of his genetic code is presented in the journal Nature by the consortium and, at first sight, it looks very similar to that of humans, consisting of about three billion or so genetic "letters", with obvious differences in only 35 million, though some segments have been shuffled. "Such a comparison will allow us to learn more about how our own genome has evolved and gain a better understanding as to why we get cancers and other diseases that chimpanzees very rarely suffer," said Dr Richard Wilson of Washington University in St Louis. The latter include HIV and Alzheimer's. "We still do not have in our hands the answer to a most fundamental question: What makes us human? But this genomic comparison dramatically narrows the search," added Prof Robert Waterston, of the University of Washington, in Seattle. When the draft human genetic code was first unravelled a few years ago, scientists were surprised to find that humans were described by far fewer genes than expected, more like 25,000 rather than 100,000 as previously thought. Today's findings show the genetic sequences of man and ape differ by only 1.2 per cent in terms of single-letter (base pair) changes to the genetic code, but duplications and rearrangements of larger stretches of DNA add a further difference of 2.7 per cent, report Dr Evan Eichler, of University of Washington School of Medicine, Seattle, and his colleagues. "For all the talk of the 1.2 per cent single base-pair difference and the importance of those, there's even more difference between the species due to duplication events," said Dr Eichler. Hotspots of genetic creativity have been found by Dr Barbara Trask, of the Fred Hutchinson Cancer Research Centre and University of Washington, Seattle, and her team in regions near the ends of chromosomes, called subtelomeres, where DNA segments changed chromosomal location and copy number very recently and there are gross differences in gene content between human and chimpanzee, as well as between human individuals. Genes usually code for proteins, the molecules that build and operate a body, and many key differences are expected to be found in genetic code that controls where proteins are made, how and in what quantities. Now scientists are looking for changes that gave our ancestors a greatly enlarged brain, the ability to walk upright on two feet, and developed their complex language skills. rhighfield@telegraph.co.uk
Previous story: Mother and children die after jumping in front of train
Next story: Breasts may be grown in lab thanks to gene find
The Chimpanzee Sequencing and Analysis Consortium, made up of 67 scientists from the United States, Israel, Italy, Germany, and Spain, has released a draft version of its report on the chimpanzee genome in the September 1 edition of the scientific journal ''Nature''.  The researchers mapped 94% of the genome.  The report centers on comparisons between chimpanzee and human DNA.