X-linked recessive inheritance

X-linked recessive inheritance is a type of genetic inheritance that is more common in males. This is because of X-inactivation, which means that females only express one of their two X chromosomes, while males only have one X chromosome.

Characteristics of the disease:

• More common in males than females: Since males only have one X chromosome, if the disease gene is located on this X chromosome, they will be affected.

• Not passed from father to son: This is because sons inherit their X chromosome from their mother.

• Disease appears intermittently across generations: This is because heterozygous females (carrying one disease gene and one normal gene) may not show symptoms, but can still pass the disease gene to their offspring.

• Heterozygous females can be affected: If X-inactivation occurs exceptionally, the X chromosome carrying the disease gene may be active, leading to heterozygous females being affected.

• Affected males, homozygous females: Males only need to carry the disease gene on their single X chromosome to be affected, while females must carry two disease genes (homozygous) to exhibit the disease.

• Normal males, heterozygous females: Heterozygous females will pass the disease gene to half of their female offspring, resulting in half of their daughters carrying the disease gene.

• Affected males, heterozygous females: Heterozygous females can pass the disease gene to both their sons and daughters, resulting in half of their offspring being affected.

Note:

• X-linked recessive inheritance can be diagnosed through genetic testing.

• There is currently no cure for X-linked recessive genetic disorders. However, genetic counseling and screening methods can help reduce the risk of developing the disease.