Pedigree Type Question

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Pedigree Type Question

Post by greenpak07 on Tue Dec 02, 2008 11:59 pm

Hi Guys,
I'm a bit confused how to approach pedigree questions like the following. I feel that either of the answers could be correct and I don't know which one to rule out. These are some sample exam questions that I don't have answers to.

A female affected with Klutzkiís disease mates with an unaffected male and has an affected daughter. Which type(s) of inheritance can be ruled out for Klutzkiís disease?
A.Autosomal dominant
B.X-linked dominant
C.Autosomal recessive
D.X-linked recessive
E.A, B and D

The second one I'm guessing is Autosomal recessive.
A girl is affected with Sleepyís disease. Both or her parents are unaffected. What is the likely mode of inheritance of Sleepyís disease?
Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive
B or D

Thanks for any help!

greenpak07
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Re: Pedigree Type Question

Post by Alla on Thu Dec 04, 2008 8:20 pm

In the first question you have affected mother x normal father and affected daughter.

If this disease (D)is autosomal dominant, you could have:

mother x father
Dd x dd would result in 1/4 Dd - affected daughter

If it is autosomal recessive (d), father could carry mutation:

dd x Dd - 3/4 offspring are affected.

If it is X-linked dominant (Xa):

XaX x XY, 25% can be XaX - affected.

However, if mutation is X-linked recessive, father would be affected since males have only one X chromosome!!!

You answered second question correctly.

Good luck!

Alla
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Re: Pedigree Type Question

Post by greenpak07 on Sun Dec 07, 2008 6:45 pm

Hi there! Thanks again for answering my questions! Smile Your a big help!

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