Question

A woman has an X-linked condition on one of her X chromosomes. This chromosome can be inherited by

• A. Only daughters
• B. Only grandchildren
• C. Only sons
• D. Both sons and daughters

Answer 1

The Correct Option is D

An X-linked condition is a genetic disorder that is linked to the X chromosome. Humans have two sex chromosomes, X and Y. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The inheritance of X-linked conditions follows specific patterns:

• Females (XX): Because females inherit one X chromosome from each parent, if a mother has an X-linked condition on one of her X chromosomes, she can pass this chromosome to her daughters. Thus, each daughter has a 50% chance of inheriting this X-linked condition.
• Males (XY): Males inherit their single X chromosome from their mothers and their Y chromosome from their fathers. Therefore, if a mother has an X-linked condition, her sons will inherit the affected X chromosome from her. Hence, every son has a 50% chance of receiving the X chromosome with the condition, making them affected if the condition is expressed with one dose of the gene (as often happens with X-linked recessive conditions).

Let's analyze the options with this understanding:

1. Only daughters: While daughters can inherit the X chromosome with the condition, they are not the only ones who can inherit it. Sons can inherit it, too.
2. Only grandchildren: Grandchildren would inherit the X chromosome only if it were passed down through a son (who cannot pass along the X chromosome received from his mother to his own male offspring, as males pass only the Y chromosome to their sons) or a daughter (who must first inherit the X chromosome, and then pass it to her offspring). However, this option doesn't directly indicate the immediate inheritance by sons or daughters.
3. Only sons: Sons do inherit the X chromosome from their mother, but daughters also can inherit the X chromosome with the condition.
4. Both sons and daughters: This option is correct because both sons and daughters can inherit the mother's X chromosome with the condition.

Based on these explanations, the most comprehensive answer is Both sons and daughters, as they both can inherit the X chromosome with the associated condition from their mother.