Both a man and a woman are affected by Vitami | vedclass

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(D) Vitamin $D$-resistant rickets is an $X$-linked dominant trait. Let $X^R$ be the dominant allele for the trait and $X^r$ be the normal recessive al

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Each parent has only one dominant allele.

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(D) Vitamin $D$-resistant rickets is an $X$-linked dominant trait. Let $X^R$ be the dominant allele for the trait and $X^r$ be the normal recessive allele.Since the woman is affected,she must have at least one $X^R$ allele. Since the man is affected,his genotype must be $X^RY$.If all daughters are affected,they must receive an $X^R$ allele from both parents. This implies the mother must be homozygous dominant $(X^RX^R)$.If the mother is $X^RX^R$ and the father is $X^RY$,all offspring (sons and daughters) would inherit the $X^R$ allele from the mother and be affected.However,the question states some sons are not affected. This implies the mother must be heterozygous $(X^RX^r)$.If the mother is $X^RX^r$ and the father is $X^RY$,the daughters will be $X^RX^R$ or $X^RX^r$ (all affected),and the sons will be $X^RY$ (affected) or $X^rY$ (unaffected).Thus,both parents possess only one dominant allele for the trait ($X^RX^r$ and $X^RY$).

Both a man and a woman are affected by Vitamin $D$-resistant rickets,which is an $X$-linked dominant trait. All the daughters of this couple are affected by rickets,but some of the sons are not. What are the genotypes of the parents?

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