A daughter has hemophilia, a recessive sex-linked trait. Which are possible genotypes of her parents?
A. XHxh and Xhy
B. XHXH and xhy
c. xhxh and XHY
D. XHxh and XHY

D. XHxh and XHY

Explanation:

since this is the only answer with genes that share a common allele, the answer is D.

In order for a recessive gene to be present, the daughter must have gained the alleles of XHXH, which in this case, is a 25% chance. The other two possibilites are XHxh, XHY, and Yxh. To further prove this, a female must have 2 X alleles and to have hemophilia, they must carry 2 H's. If they were to only have one H, they would be a carrier instead of a product.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.