bluntknife
Forum Senior
Topics: 8
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A 30 yr old man is phenotypically normal but two of his siblings died from tay-sachs disease,an autosomal recessve condition that is lethal by age 5....what is the risk that the man is a heterozygous carrier of the disease causing mutation?
A. 1/4
B. 2/3
C. 1/2
D. 3/4
E. not elevated above that of the general population
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| doc179
Forum Guru
Topics: 67
Posts: 1,217
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B
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| sarika
Forum Guru
Topics: 195
Posts: 1,200
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C.
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| bluntknife
Forum Senior
Topics: 8
Posts: 80
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B. is the right answer.....the genotypes as from 2 by 2 table can be
AA,Aa,Aa and aa......since he did not develop the disease so that rules out aa.....so the best answer is 2/3 good job doc179
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| doc179
Forum Guru
Topics: 67
Posts: 1,217
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his parents were both Aa.
He could have been AA, aa or Aa or aA.
He is phenotypically normal, so we know he is not aa.
So he could now be AA, Aa or aA.
What are his chances of being heterozygous carrier?
Two out of three.
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| sarika
Forum Guru
Topics: 195
Posts: 1,200
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Thankyou 
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