Question

a male is more likely than a female to express a dominant trait that is carried on the x chromosome. true false

Explanation:

Males have one X chromosome (XY), while females have two (XX). For a dominant X - linked trait, a female needs the dominant allele on at least one of her two X chromosomes to express the trait. A male only has one X chromosome, so if that single X has the dominant allele, he will express the trait. However, if the trait is X - linked dominant, females actually have a higher chance of expressing it. Because females have two X chromosomes, they have two opportunities to get the dominant allele. Males have only one X. For example, if the mother is heterozygous (X^A X^a) for an X - linked dominant trait:

• The probability that a son (XY) gets the X^A (and thus expresses the trait) is 0.5.
• The probability that a daughter (XX) gets at least one X^A (and thus expresses the trait) is \(1-(0.5\times0.5) = 0.75\) (using the complement rule: probability of not getting the dominant allele on either X is \(0.5\times0.5\) for a daughter, so probability of getting at least one is \(1 - 0.25\)).

Answer:

False