Two parents have a child with hemophilia. What must be true about the parents of

Question

Two parents have a child with hemophilia. What must be true about the parents of the child? Please make sure you understand the meaning of the word "must" before attempting this question. If the child is male at least one parent had hemophilia This does not have to be true. The child could have obtained the Y from an XHY father (no hemophilia) and the Xh-A from his mother who could be a carrier (Xh-A XH) and thus not have hemophilia.

If the child is male, both parents had hemophilia

If the child is female, the mother is neither a carrier nor a hemophiliac

If the child is male, the father must have had hemophilia

If the child is female at least one parent must have had hemophilia

Explanation / Answer

Correct answer:

If the child is female, at least one parent must have had hemophilia.

Hemophilia is inherited in an X-linked recessive pattern. The genes associated with hemophilia are located on the X chromosome.

Male has one X chromosome which comes from mother. So, if male child gets hemophilia, he inherited defective allele from mother.

Female has two X chromosomes. Out of which one comes from mother and another comes from father. So, if female child gets hemophilia, she inherited defective allele from both mother and father. We know that father has one X chromosome and has defective allele. It means he has hemophilia. Mother can be carrier or affected.

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