Question

Males are less likely to survive than females, both before and after birth. One important reason is that

a. Males have more dominant, defective alleles than females.
b. Males are more vulnerable to disorders caused by X-linked recessive alleles than females.
c. Males have two Y chromosomes.
d. Most societies value males less than females and provide males with less protection.

Answer 1

Males are more vulnerable to X-linked recessive disorders because they possess only one X chromosome, expressing any recessive allele present. Females with one normal and one mutant allele are carriers and often asymptomatic, but they can pass the affected allele to their offspring, leading to more frequent occurrences in males.

Step-by-step explanation:

The reason males are more likely to exhibit disorders associated with X-linked recessive alleles is because they have only one X chromosome. Unlike females, who have two X chromosomes and must inherit two copies of the recessive allele to express the trait, males need to inherit just one recessive mutant allele on the X chromosome to be affected. This is evidenced in disorders such as red-green color blindness, and hemophilia A and B.

Females who carry one recessive mutant allele for an X-linked trait and one normal allele are carriers and often unaffected. However, they can pass on the affected allele to their sons, who then express the condition, or to their daughters, who then may become carriers. Thus, due to this genetic mechanism, X-linked recessive disorders are seen more frequently in males.