Does age at conception affect passing on the gene?
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Q. My grandfather had HD and my father, who is in hos mid 40’s is showing signs of it. I was conceived when my father was only 16 years old. Does his age at conception affect the possibility that I may or may not have the HD gene?
Natalia, Young Adult, USA
A. Dear Natalia,
Thank you for your question.
Parental age at conception does not alter the 50:50 chance for a child of someone who carries an HD gene expansion, so the fact that your father was 16 when you were conceived will not change your own chance of having the HD gene.
Although the 50:50 chance is the same when passed on by a father or a mother, you may have read that the HD gene expansion can be slightly more unstable when passed on by a father, so if a child inherits the HD expansion it can occasionally be bigger (or sometimes smaller). Even so, this is relatively uncommon, and we usually find that a child inherits the same size expansion even if they inherited it from their father. There is no evidence that paternal age at conception makes a change in expansion size any more (or less) likely to happen.
I hope that helps to answer your question, but please do not hesitate to get back in touch if you have any other queries.