It has long been recognized that certain genetically influenced conditions presenting in childhood such as intellectual disability and autism are more common in children from older fathers. A possible explanation for this phenomenon was described recently in a study suggesting that fathers accumulate and pass on mutations at a faster rate with increasing age than mothers.


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In a research study from Iceland, published in Nature, researchers sequenced the genomes of 14,000 Icelanders and their parents, isolating de novo mutations and determining the parent of origin.

They found that whilst the number of de novo mutations inherited from mothers increased by 0.37 per year of age, the number inherited from fathers increased by 1.51 per year of age.

An article in The Guardian reporting the study commented that these figures mean that ‘a child born to 30-year-old parents would, on average, inherit 11 new mutations from the mother, but 45 from the father’. And this discrepancy would only further increase with increasing age.

The authors hypothesize that one explanation for this could be that whilst women are born with their eggs already in situ, men continue to make sperm throughout their lives, during which time more mutations can accumulate.