X-linked dominant conditions are expressed in both males and females. These conditions are generally more severe in males. Explain how.

X-linked dominant conditions are caused by mutations in genes located on the X chromosome. Since males have only one X chromosome (in addition to their Y chromosome), they are more likely to be affected by X-linked dominant conditions because they do not have a second, healthy X chromosome to compensate for the mutated one.

In females, who have two X chromosomes, the presence of a healthy X chromosome can often mask the effects of the mutated X chromosome. This is known as X-inactivation, where one of the X chromosomes in each cell is randomly turned off. As a result, females may have a milder form of the condition or may not show any symptoms at all.

In contrast, males do not have a second X chromosome to compensate for the mutated one. As a result, they are more likely to exhibit the full effects of the X-linked dominant condition, making the condition generally more severe in males. This is why X-linked dominant conditions are often more severe in males compared to females.

X-linked dominant conditions are caused by mutations in genes located on the X chromosome. Males have only one X chromosome, while females have two. This means that males are hemizyguous for X-linked genes, while females are heterozygous.

In the case of an X-linked dominant condition, a single copy of the mutated gene is sufficient to cause the condition. This means that males who inherit the mutated gene from their mother will be affected, regardless of whether their father carries the mutation. Females who inherit the mutated gene from their mother will be carriers, meaning that they will not be affected themselves but can pass the mutation on to their children.

X-linked dominant conditions are generally more severe in males than in females. This is because males have only one copy of the X chromosome, and therefore only one copy of the gene responsible for the condition. Females, on the other hand, have two copies of the X chromosome, and therefore two copies of the gene. This means that females are less likely to have a severe form of the condition, as they have a backup copy of the gene that can compensate for the mutated copy.

Examples of X-linked dominant conditions include:

- Vitamin D-resistant rickets
- X-linked hypophosphatemia
- X-linked agammaglobulinemia
- X-linked spinal and bulbar muscular atrophy