Question

Pattern baldness is a sex-linked recessive trait. If a woman whose father is bald and a man who is bald have a son and the womans mother does not carry the allele for pattern baldness. The probability that the son will inherit the allele for pattern baldness is

• A. 0%
• B. 25%
• C. 50%
• D. 75%
• E. 100%

Answer 1

The correct option is C 50%

Pattern baldness is a sex-linked recessive trait, which indicates that it is carried on the X chromosome. A female inherits one X chromosome from her father. Because the woman’s mother does not carry the allele for pattern baldness, the woman only carries one copy of the allele. If the couple has a son, there is a 50% chance that the son will inherit the X-linked allele for pattern baldness from his mother. The father’s baldness is irrelevant; he will pass his unaffected Y chromosome to the son.