Women who inherit a 'flipped' version of a section of DNA are likely to have more children than those who inherit the standard version, Icelandic researchers say. The 'H2 inversion', discovered by scientists at Reykjavik-based biotech firm DeCode Genetics, is common in Europeans, quite rare in Africans and virtually absent in Asians. An inversion is a type of chromosome rearrangement, in which a section of chromosome is removed, turned upside down and reinserted back into its original place. The piece of genetic material involved is around 900,000 base-pairs (chemical units of DNA) in length, but flipping it around appears to have no other effect.
The scientists came across the inversion whilst looking for a gene involved in schizophrenia on chromosome 17, which turned out not to be there. The section of DNA they studied did not match the published version of the human genome, suggesting a rearrangement of some sort. Around 20 per cent of Icelanders have at least one copy of the inversion say the team, who published their findings in the journal Nature Genetics. About 21 per cent of all Europeans have the H2 inversion, but only six per cent of Africans and one per cent of Asians carry the rearrangement.
The researchers say that with each generation, female carriers of the H2 inversion have about 3.2 per cent more children than women who do not have the inversion. Such a reproductive advantage could have 'profound consequences on evolution', say the team. The inverted section of DNA contains several known genes, but none have any 'obvious' connection to fertility. However, it seems that the inversion is linked to higher rates of 'genetic shuffling' between generations, which could account for its reproductive benefits. The inversion also seems to confer the ability to live to a ripe old age - it is more common in women over 95 and men over 90, according to DeCode chief executive Kari Stefansson.
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