In the pedigree below, 4 individuals have vitamin-D resistant rickets (X-linked
ID: 37461 • Letter: I
Question
In the pedigree below, 4 individuals have vitamin-D resistant rickets (X-linked dominant with P=0.8).
The probability that individual III-1 would suffer from vitamin-D resistant rickets is: . . . . .The probability that the III-2 would suffer from vitamin-D resistant rickets is: . . .
In the pedigree below, 4 individuals have vitamin-D resistant rickets (X-linked dominant with P=0.8). The probability that individual III-1 would suffer from vitamin-D resistant rickets is: . . . . .The probability that the III-2 would suffer from vitamin-D resistant rickets is: . . .Explanation / Answer
The probability that individual III-1 would suffer from vitamin-D resistant rickets is 0%The probability that the III-2 would suffer from vitamin-D resistant rickets is 100%
since:
In X-linked dominant inheritance, when the mother alone is the carrier of a mutated, or defective gene associated with a disease or disorder; she herself will have the disorder. Her children will inherit the disorder as follows:
1- Of her daughters and sons: 50% will have the disorder, 50% will be completely unaffected. Children of either sex have an even chance of receiving either of their mother's two X chromosomes, one of which contains the defective gene .
When the father alone is the carrier of a defective gene associated with a disease or disorder, he too will have the disorder. His children will inherit the disorder as follows:
1- his daughters: 100% will have the disorder, since all of his daughters will receive one copy of his single X chromosome.
2- his sons: none will have the disorder; sons do not receive an X chromosome from their father.
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