X-linked traits are characteristics determined by genes located on the X chromosome. Since males have one X chromosome and one Y chromosome, they are more likely to express X-linked traits, even if they inherit just one copy of the gene. In contrast, females have two X chromosomes, so they need two copies of the gene to express the trait. Common examples of X-linked traits include color blindness and hemophilia. If a father has an X-linked trait, he will pass the gene to all of his daughters but none of his sons, as sons inherit their Y chromosome from their father.