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Thursday, February 12, 2009

Repeats, deletions and other rare mutations separate humans and chimps

at News Daily. Original paper by H. Huges et al. published in Nature.

According to this research it was not normal mutations (i.e. the change of G into T or similar, known as SNPs) which caused the rapid divergence between great apes and monkeys and, later on, also humans from great apes. Instead these were apparently caused by copy number variations, including sequence repeats, deletions and even reversions. These kind of mutations are often associated to dieseases in humans but may have also been the origin of species divergence.

As expected, they found humans and chimps were very close in terms of overall sequence. The main differences lie in copy number variations -- repeats of the same genetic sequence over and over, deletions of the sequence, or even instances in which a sequence runs backward.

Among humans, these variations have been associated with diseases ranging from AIDS to autism. They may also underlie the differences between species, Eichler said.

The analysis suggested that in the ancestral branch of primates leading to humans and the African great apes, the number of these duplications began to increase at the same time that the more classic genetic mutations were slowing down.

Humans and chimps, in particular, tend to have extra copies of these sequences, they reported.

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