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#1
03-11-2015
 USMLE Forums Scout Steps History: CS Only Posts: 48 Threads: 33 Thanked 2 Times in 2 Posts Reputation: 12
Genetics Question..plz help!

Im having difficulty understanding the following question from Kaplan genetics chapter 2 review questions: (sry tried uploading the image but it isn't working)

8. A man who is a known carrier of oculocutaneous albinism marries his half cousin (they share a common grandparent). This trait is transmitted as a fully penetrant autosomal recessive. What is the probability that this couple will produce a child with this disorder?

A. 1/2
B. 1/4
C. 1/8
D. 1/16
E. 1/64

**how do v calculate the probability of wife being a heterozygote/homozygote when her parents and grandparents are shown phenotypically normal in the pedigree??

#2
03-11-2015
 USMLE Forums Addict Steps History: Not yet Posts: 147 Threads: 18 Thanked 49 Times in 30 Posts Reputation: 59

i will try without cheating.

Aa[aa+AA+Aa]=the cousin can have three probabilities AA,Aa,aa i will assume the cousin has no albism which is somehow implied in the question therefore i will reduce it to

Aa[Aa+AA]=AaAa+AaAA=1/4+0=1/4

a=recessive allele
A=dorminant allele

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