Dr_Cosme
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D) since 1/4 (25%) will express the disease, you have left 3/4 healthy offsprings. out of those 2/3 are heterozygous carriers.
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| jean robert
Forum Guru
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C
For AR disease, 25% will express disease; 25% will be healthy and 50% are heterozygous carrier.
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| Dr_Cosme
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excuse mois sil vous plait' aren't these heterozygous carriers healthy?
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| jean robert
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Sure, heterozygous carriers won t be affected. In my post, i actually mean that 25 % won t inherit any copy of the disease gene at all.
Let s go back to question.
First of all, well done, Dr_cosme.choice D (2/3) seems most likely to be the correct answer. .
But to a similar question in kaplan Qbank, here is the explanation that they provide:
"To be an asymtompmatic patient for a AR disease, 3 scenarios are possible:
1.-He inherited no copies of the mutation
2.-He inherited a copy from his father
3.-He inherited a copy from his mother
Each of these 3 posibilities is equally likely , and 2 of them lead to heterozygosity.
Thus, the probability that asymptomatic brother or sister of a child with a AR dz is a heterozygous carrier is 2/3."
Do u think this explanation is adequate for this particular question?
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| Dr_Cosme
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I see what is wrong, they were asking for heterozygous carriers,  Thanks man and great explanation.
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