Question

During very early development of mammalian females, one of the two X-chromosomes normally present in each somatic cell becomes deactivated. Deactivation is random, with maternal and paternal X-chromosomes equally likely to be deactivated. All cells deriving from this cell carry the same deactivated X-chromosome, creating local patches of tissue with either maternal or paternal features. Anhidrotic ectodermal dysplasia (AED) is an inherited skin condition caused by the recessive allele (s) of a gene that has its locus on the X-chromosome. In some individuals with this condition, sweat gland distribution is patchy, with some areas lacking glands. In other individuals with this condition, all sweat glands are absent. Which one of the following is consistent with the information given?

A. Patchy sweat gland distribution is found in males and females but is more likely in males with the condition.

B. Patchy sweat gland distribution is equally likely in both males and females with the condition.

C. Only females with the condition exhibit patchy sweat gland distribution.

D. Only males with the condition exhibit patchy sweat gland distribution.

Answer 1

Only females with Anhidrotic ectodermal dysplasia (AED) exhibit patchy sweat gland distribution due to X inactivation. Males with AED do not have patchy sweat gland distribution because they have only one X chromosome, so effects of the condition would be uniform throughout the skin if they are affected.

Step-by-step explanation:

The correct answer to the question of whether patchy sweat gland distribution due to Anhidrotic ectodermal dysplasia (AED) occurs in males or females with the condition is that only females with the condition exhibit patchy sweat gland distribution. This is because the mechanism behind the patchy distribution is X inactivation, which occurs only in females. In males, who have only one X chromosome, a recessive gene resulting in AED would affect all cells, leading to a uniform absence of sweat glands, provided they have the mutated gene on their single X chromosome.

X inactivation is a process where one of the two X chromosomes in females condenses into a Barr body, and this inactive chromosome is passed down to all descendant cells. As a result, patchy distribution of characteristics can be observed in females, such as in the case of AED and the trait's expression being varied depending on the X chromosome that is inactivated. Since males have only one X chromosome, there can't be random inactivation leading to patchy expression, therefore males cannot have a patchy distribution of sweat glands caused by AED.