Question

Which of the following statements is true with reference to X-linked recessive traits in human beings?

• A. They express equally in both the sexes.
• B. They express more in males than in females.
• C. They express more in females than in males.
• D. They express only in males.

Answer 1

Answer: (B)

They express more in males than in females.

In X-linked recessive inheritance, a mutation in a gene on the X chromosome causes the phenotype to be expressed in males (because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation. X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. Carrier females who have only one copy of the mutation do not usually express the phenotype, although differences in X chromosome inactivation can lead to varying degrees of clinical expression in carrier females since some cells will express one X allele and some will express the other. Thus, option B is correct and other options are wrong.