Basic Concepts of Probability: Videos & Practice Problems

Males have $\text{XY}$ chromosomes, and females have $\text{XX}$ chromosomes. $\text{X}$-linked recessive traits (such as red-green color blindness) appear when a defective $\text{X}$ chromosome is not paired with a healthy $\text{X}$. Represent the defective $\text{X}$ chromosome with $\text{x}$, so a child with $\text{xY}$ or $\text{Yx}$ will express the trait. A child with $\text{XX}$, $\text{XY}$, $\text{YX}$, $\text{xX}$, or $\text{Xx}$ will not express the trait. Each parent passes one of their chromosomes to the child. What is the probability that a son will exhibit the trait if the mother has one faulty $\text{X}$ chromosome and the father has normal $\text{XY}$ chromosomes?