If a mother has one dominant allele for a disease on her X chromosome, what is the likelihood her sons and daughters will inherit the disease?

The likelihood of a son or daughter inheriting a disease from a mother with one dominant allele on her X chromosome depends on whether the disease is X-linked or not.

1. If the disease is X-linked:

   • Sons: A son has a 50% chance of inheriting the disease. This is because sons receive their X chromosome from their mother and their Y chromosome from their father. If the son receives the X chromosome carrying the dominant allele for the disease, he will have the disease.
   • Daughters: A daughter has a 50% chance of being a carrier of the disease. This is because daughters receive one X chromosome from their mother and one X chromosome from their father. If the daughter receives the X chromosome carrying the dominant allele for the disease from the mother, she will be a carrier. However, she will typically not express the disease unless it is a dominant trait and the father also carries the allele for the disease on his X chromosome.

2. If the disease is not X-linked:

   • Both sons and daughters have a 50% chance of inheriting the dominant allele for the disease from their mother. However, whether they express the disease depends on the allele they inherit from their father and whether the disease is a dominant or recessive trait.