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Why sex makes sense, evolutionarily

23 February 2015

By Sophie McLachlan

Appeared in BioNews 791

Humanity's predisposition to disease has been reduced thanks to hundreds of generations of sexual reproduction, research shows.

The study, published in Nature Genetics, is one of only a few to furnish hard evidence of the genetic benefits of sexual – as opposed to asexual – reproduction. It suggests that the mixing of genetic material over time decreases the number of disease-causing mutations within our genomes.

Dr Philip Awadalla, from the University of Montreal, Canada, who led the study, said: 'This discovery gives us a better understanding of how we, as humans, become more or less at risk of developing or contracting diseases.' 

The research relies on the fact that when male and female chromosomes intertwine during sexual reproduction to produce the offspring's DNA, this 'genetic recombination' does not happen uniformly across the genome.

Some sections in our chromosomes are what the researchers called 'coldspots', where relatively little genetic recombination takes place.

The scientists analysed the genomes of over 1,400 people who had had their DNA sequenced for the CARTaGENE and 1,000 Genomes projects. They found that these coldspots harboured a higher proportion of disease-enabling mutations. Also dangerous mutations were generally more damaging when found in the coldspots, as compared to the mutations found elsewhere in the genetic code.

A statement from the scientists added that the results also tell scientists 'more precisely where to look in the human genome to find disease-enabling mutations', which could 'speed up the discovery and identification of mutations associated with specific diseases'.

This is, however, contentious. For researchers looking for diseases-causing genes, it seems unlikely that neglecting sections of the genome would reap much benefit when the rapidly plummeting cost and difficulty of whole genome sequencing is taken into account.

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