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Need help in an assignment

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Need help in an assignment

Postby dreamtim » Sun Sep 09, 2012 12:39 pm

hallo everyone

I have a question in which i need to find out what is the most
suitable heredity system to a rare disease.

the answers are:
1.x linked recessive
2.x linked dominant
3.autosomal recessive which appears only in males
4.autosomal dominant which appears only in males
5.y linked recessive

thanks you very much for you help!

p.s-i've attached the pedigree
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Postby Cat » Sun Sep 09, 2012 1:45 pm

The best answer is 3.autosomal recessive which appears only in males.

It cannot be sex liked. It's not X-linked because that scenario it would NOT be passed from father to son and it is. It's not Y-linked because in that case, it would ONLY be passed from father to son (not the case here). It cannot be dominant because that requires that at least one parent of each affected individual be also affected. Again, not in this case. So, that leaves #3...
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Postby dreamtim » Sun Sep 09, 2012 4:05 pm

first of all thanks, second I also thought that this is the answer, but my doctor published her answers and according to her the answer is 4-autosome dominant which appears only in males.
that means the first male must be homozygote recessive and the first female must hetrozygote, but as we can see she isn't a carrier.
So if my doctor is right, could it be that the female is not marked in black because this affect only males? I mean this is possible that one sex have a dominant allele but becase the sex it doesn't appears?
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Postby Cat » Sun Sep 09, 2012 4:19 pm

I suppose that is possible theoretically. However, this pedigree in itself is insufficient to conclude one way or another. Also, you did not provide what condition we are talking about. Is it something male-specific? If you want, provide the link to publication you are talking about so we could discuss some more...
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Postby dreamtim » Sun Sep 09, 2012 5:03 pm

I provided all the data that was given...
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Postby Cat » Sun Sep 09, 2012 5:58 pm

Than I would say #3 based on information provided. The only male specific autosomal dominant condition I know about is male infertility. Judging by pedigree it's not that...
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Postby dreamtim » Mon Sep 10, 2012 9:56 am

jajajaja:))
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Postby JackBean » Mon Sep 10, 2012 4:07 pm

If it was recessive, you would see the pattern of every-other generation, but you see affected people in every generation, thus it is dominant affecting only men (and that's the reason, why you do not see affected parents of affected children)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Re:

Postby Cat » Mon Sep 10, 2012 7:01 pm

JackBean wrote:If it was recessive, you would see the pattern of every-other generation


Why do you say that? This is autosomal, not sex chromosome. Why would you expect this pattern?

My only concern with this being a recessive mutation is high frequency of mutant allele in general population...
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Re: Need help in an assignment

Postby dreamtim » Tue Sep 11, 2012 9:43 am

i don't understand, if it is dominant then i should see affected parents and affected children, no?
and how is that autosomal gene affect only males?
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Postby JackBean » Tue Sep 11, 2012 10:17 am

If it's related to something male-specific, then you will hardly see it in women (as the mentioned sperm production). And in such case, although mother should be affected, you do not see it, so she seems like healthy, although she's not.
http://www.biolib.cz/en/main/

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Re:

Postby Cat » Tue Sep 11, 2012 2:39 pm

JackBean wrote:If it's related to something male-specific, then you will hardly see it in women (as the mentioned sperm production). And in such case, although mother should be affected, you do not see it, so she seems like healthy, although she's not.


That is the main problem. It's not sperm production as males are fertile according to pedigree. It's said to be a rare disease, so can you think of any male specific disease that autosomal? I sure cannot think of anything.
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