What defines a sex-linked condition?

A sex-linked condition is defined as a condition that is associated with genes located on the sex chromosomes, particularly the X and Y chromosomes. The most commonly referenced sex-linked conditions are those linked to the X chromosome, as it carries a significant number of genes relevant to traits and conditions, while the Y chromosome is smaller and carries fewer genes.

When considering option B, it correctly describes a common inheritance pattern of X-linked conditions, which are typically passed from carrier mothers (who have one affected X chromosome) to their sons. Sons inherit their X chromosome from their mothers, meaning that if a mother carries a recessive trait on her X chromosome, there is a chance she will pass it to her son, who will express the trait since he does not have another X chromosome to potentially mask that effect.

Understanding this inheritance pattern is crucial, as it highlights the role of females as carriers and the direct implications this has for male offspring, who are more likely to express certain X-linked conditions. This information also illuminates why conditions such as hemophilia and color blindness primarily affect males, as they inherit their single X chromosome from their mother.