I know that DMD is passed on from mom if she is a carrier. I have not had genetic counseling and I have done some research on the internet, but I have a strange situation. I do not know if I am a carrier because we have had some trouble with Riley's bloodwork and I was waiting for his before I get tested. The funny thing is, there is no MD on my mother's side of the family and I do not have brothers, but there are a lot of relatives on my father's side with DMD and other types of MD! My father has about 6 cousins with MD. 3 were brothers who all had DMD, one other had DMD, one had another type (unsure) and as of last month he had another counsin diagnosed with MD! Is it EVER possible to have a male carrier or is this all just a crazy coincidence? Any thoughts?

Views: 227

Reply to This

Replies to This Discussion

The video someone already mentioned can explain better than I can but each child of a carrier has a 50 50 chance of having or not having DMD so it is possible to be in the family for a long long time and never actually show up.Every boy in the family had a 50% chance of having DMD and a 50% chance of not having it. Just as a girl would have a 50% chance of being a carrier and a 50% chance of not being a carrier
Men pass on the Y chromosome to boy children, and the X chromosome to girl children. It is the man who determines what sex the child will be by passing on either the X or the Y chromosome.

DMD is on the X chromosome. That means it is possible that a man can pass it on to a female child. However, it would be obvious that the father had it. There is not any "hidden" or "recessive" DMD gene that men can have that I am aware of. This is because they only have one X chromosome, and if it is messed up it would be apparent (in the form of DMD). In contrast, because women have two X chromosomes, one of them could be mutated but the healthy one makes up for it and they would not have symptoms or they would be so mild that they don't look like a full-fledged DMD (e.g., some carriers have heart problems when they get to be in middle adulthood).

That is my basic understanding of the process, but a genetic counselor could probably tell you more.
Hi,
I've actually done a lot of research into this.

Christian's right - a man can be a germline carrier the same way that a woman can. So a man would pass on a bad x via sperm only to a baby that would then be a female carrier. That still doesn't explain Rhainnon's situation, though. I'd be really curious about whether the mutations differed.

Tanya - if you're the first carrier in your family, I would bet money that your mom is a germline carrier. So there aren't any other carriers in the family because your siblings came from eggs without the mutation.

I would caution anyone to put too much faith into the statistics that we're quoted by the geneticists. I now know of three people that have done IVF with PGD, including myself. Two of us are germline carriers, and had 15% and 75% of eggs affected. One person I know if is a true carrier, and she had 67% of her eggs affected. So that 50/50 can be much higher. I think the bottom line is that no one can really tell us what our risk of additional affected children is.
http://www.mda.org/Publications/Quest/q81ss.html

Here is an article that explains germline mosacism that might be of interest.
The 67% doesn't surprise me at all. We are talking about 1, 2 samples from her eggs, so the percent doesn't need to be 50. On the average, if a large enough number of samples from a female carrier is taken, the percent will get closer and closer to 50%.

The non-carrier situation is quite difficult. As my son's doctor said, any of us non-carriers can have ANY number of eggs affected. I keep wondering, when they write on these DNA test results "there is a slight but real possibility that X is a germline carrier", what do they base the "slight" on? Do they just look at the number of non-carrier families having a 2nd child affected, and that number is quite low? Also, when they say that there can be spontaneous mutations, is that really based on evidence? Do they have documented cases having done IVF/PGD when none of the eggs carried the mutation? So far I haven't heard about any such case. It is true that in many non-carrier families only one child has DMD/carries the mutation, but that definitely doesn't imply a spontaneous mutation.



Mindy said:
Hi,
I've actually done a lot of research into this.

Christian's right - a man can be a germline carrier the same way that a woman can. So a man would pass on a bad x via sperm only to a baby that would then be a female carrier. That still doesn't explain Rhainnon's situation, though. I'd be really curious about whether the mutations differed.

Tanya - if you're the first carrier in your family, I would bet money that your mom is a germline carrier. So there aren't any other carriers in the family because your siblings came from eggs without the mutation.

I would caution anyone to put too much faith into the statistics that we're quoted by the geneticists. I now know of three people that have done IVF with PGD, including myself. Two of us are germline carriers, and had 15% and 75% of eggs affected. One person I know if is a true carrier, and she had 67% of her eggs affected. So that 50/50 can be much higher. I think the bottom line is that no one can really tell us what our risk of additional affected children is.

Reply to Discussion

RSS

Need help using this community site? Visit Ning's Help Page.

Members

Events

© 2020   Created by PPMD.   Powered by

Badges  |  Report an Issue  |  Privacy Policy  |  Terms of Service