Fertility researchers have traditionally focused on the impact of the mother\’s age on children\’s health, because sons and daughters of older women are known to be at higher risk of Down\’s syndrome and other, rare disorders.
But a landmark study in the Nature journal has shown that most genetic mutations which arise in children are passed down by the father\’s sperm rather than the mother\’s eggs.
Kari Stefansson, senior author of the study by DECODE Genetics, an Icelandic company, said: \”All areas of the human genome were a mutation once upon a time, so all human variety is down to a mutation.
\”But one interesting aspect of this work is it shows us that the classic focus on the age of the mother and the health of the child is not sufficient.
\”The increasing age of the father has a much bigger impact on a child\’s health in a general way. Women are off the hook and we men are on it.\”
Perfectly happy with the idea of the basic research: mutations increase with the age of the man. But I\’m not entirely convinced by the conclusion as it is being presented.
This might be just because I\’m being a pendant but I do think there\’s a point here. As ever, correct me where I err.
As far as I\’m aware, the rate at which conception leads to say, Down\’s syndrome, doesn\’t change over the ageing of a woman. It\’s the rate (umm, chances of?) implantation, the non-rejection by the womb of this flawed foetus, which does change. One description put it in game theoretic terms almost. When young there will be many more chances to conceive a better foetus so rejection of flawed ones is a good use of the huge resources required to bring a pregnancy to term. The older the woman gets the fewer such chances there will be so loosening the standards of rejection makes sense. Worth taking the risk of bring imperfection to term despite the use of those resources as they\’ll not find an alternative foetus to be used on (replace foetus with blastocyst whatever to make sense here).
It is, if you like, analagous to the whole sex thing itself: men continually proffer and women decide whether it happens or not. Conception happens a great deal more than live birth and it\’s the woman (not consciously of course) who decides. And the standards by which that decision gets made alter with age.
Which means that sure, there could well be a rise in mutation rate in sperm as the man ages. But that isn\’t the determinant of a rise in the mutation rate of live births……