Y chromosome mutation and Alzheimer's question

[familydar]

There have apparently been studies (thank you Google) suggesting that men who lose their Y chromosomes with age may have an increased risk of developing Alzheimer's.  If the chromosome can be lost, does anybody know if it can also become damaged/mutated prior to disappearing?  Google's not so helpful in this respect.  Two men, paternal first cousins, are estimated by FTDNA to have only a slightly less than 30% chance of sharing a common ancestor within two generations.  However as both men are victims of this disease of old age I wonder if the DNA that was tested could have differed from that of their youth.

Please note I'm not suggesting that l agree or disagree with the studies, I'm not qualified to have an opinion, my interest is in the fact that the Y chromosome might possibly mutate during a man's lifetime and somebody reading this may know for definite whether it does.

I've considered an NPE but as the Y-testing says it has to be a family member, the only candidate possibly in the frame would be their own great-grandfather with his daughter in law (added for clarification).  At that distance the FTDNA estimate is still on the wrong side of 50%.

Autosomal comes out as first cousins or uncle/nephew.

Jane :-)

[Seaton Smithy]

A man's y chromosome can mutate during his lifetime and studies do indicate that an increased risk of new variants does correlate to the age of the father at the conception of the child.

What Genetic Distance are these two second cousins?

[familydar]

Hi SeatonSmithy and thanks for your response.

The men are first cousins, DNA genetic distances as follows:
FTDNA Y37 GD1 at 37 markers
FTDNA family finder (autosomal) 1st cousin, uncle/nephew
GEDMatch (autosomal) 2.1 gen

At time of conception of their various children all of the men were in their 20s or 30s except for the grandfather, who was 40 when his last child, the father of the younger cousin, was conceived (33 for the other one).  WW1 put paid to him at the age of 49 so we don't know if he might have developed any disease of old age.  And his early death means he can't have fathered either of the cousins.

The grandfather himself was born to the youngest father - only 20 - which is why I wonder if that man might be in the frame for a close encounter with his daughter in law.  Although there were at least five live births to this young man and his wife, only the first two survived beyond infancy.  But by the time his oldest son had grown up and married, any medical condition which he might have picked up in his youth would have cleared up, and if it didn't leave him sterile and he was still capable then who knows what he might have got up to?

Jane :-)

[Seaton Smithy]

The men are first cousins

OK, I was confused when you said the candidate was their great-grandfather.

A GD=1 at 37 markers would seem unusual, but I guess mutations have to happen somewhere.

[familydar]

mutations have to happen somewhere

Thanks for your very diplomatic reply.  When I'm feeling rational (which thankfully is most of the time I think), that's my conclusion too.  But I was one of those kids who was always asking "why?" and I don't seem to have grown up yet!

If anyone else has any observations or suggestions I'd be glad of their input.

Jane :-)