Geneticists have long said that humans and chimpanzees, the closest living relative of the humans, share 98.5 % of their DNA; but Uppsala University researchers have investigated which parts of the genetic material is missing in one species or the other. The specific DNA sequences encode protein or protein variants that other species lack and vice versa.

Well, the new study concludes that the total DNA variation between humans and chimpanzees is rather 6-7 %. There are obvious similarities between chimpanzees and humans, but also high differences in body structure, brain, intellect, and behavior etc. In the 4 to 7 million years since the human lineage split off from chimpanzees lineage, a lot of mutations operated on the human genome. To understand the evolutionary history of humans and chimpanzees is very important to spot distinct traits crucial to the development of the species and their unique features.

The Swedish researchers have compared the DNA sequence from chromosome 21 in humans and chimpanzees to locate where the genetic differences occur and which is their importance. The researchers found that - indeed - in 1.5 % of the genetic material a nucleotidic base (genetic letter) has been replaced by another nucleotide. But also more than 5 % of the DNA is specific to only one of the species, thus certain proteins can not be produced by the other species, or at least not in the same variant. And in both species, the genome has added or lost DNA. Thus, the total difference is estimated at over 6.5 %.

Even if most of the differences are found, as expected, in the so called " junk DNA" that does not encode genes (but is important in tuning genes activity); pieces of DNA have been added or lost in 13 % of the genes. "It is probable that a species can compensate for this by producing a similar protein from another part of the gene, but some of these differences have clearly been crucial to the development of the species," says Tomas Bergstr�m, lead researcher.