Question

Duchenne muscular dystrophy is a genetic disorder that arises from a recessive X-linked allele. Why is this disorder almost always restricted to males? A. Males have XX chromosomes and therefore have a higher chance of carrying both recessive alleles for this genetic disorder. B Females have XX chromosomes and therefore have a very low chance of carrying both recessive alleles for this genetic disorder. C. Females have XX chromosomes and therefore have a higher chance of carrying both recessive alleles for this genetic disorder.

Answer 1

I think the correct answer from the choices listed above is option B. This disorder is almost always restricted  to males because females have XX chromosomes and therefore have a very low chance of carrying both recessive alleles for this genetic disorder.

Answer 2

The correct answer is B.

There are two types of sex chromosomes, the X and the Y.

Males have the XY combination and females have the XX combination of sex chromosomes.

When a condition is X liked recessive it means that in order for the disease to be present, he individual has to have ALL of the X chromosomes with the recessive allele. In females, that means that the diseased individual will have recessive alleles on both of the X chromosomes. In males, it means that the one and only X chromosome has the recessive allele.

From this information, it is evident that is harder for female to develop the disease, since two recessive alleles are necessary. On the other hand, only one recessive alleles will cause the disease in males.