In sex-linked inheritance, the abnormal gene is carried on the X chromosome.

Sex-linked inheritance refers to the inheritance of genes located on the sex chromosomes, which in humans are the X and Y chromosomes. As females have two X chromosomes and males have one X and one Y chromosome, sex-linked traits are typically inherited in different patterns in males and females. If an abnormal gene is located on the X chromosome, it can be passed on to offspring by both males and females, but males are more likely to express the trait as they have only one X chromosome.