Final answer:
The probability of a son being affected by an X-linked recessive trait from a carrier mother is 50 percent, while daughters will not be affected but have a 50 percent chance of being carriers.
Step-by-step explanation:
When considering the inheritance of X-linked recessive traits, the probabilities vary for sons and daughters. If a mother has an X-linked recessive trait, her sons have a 50 percent chance of being affected because they inherit one X chromosome from their mother and a Y chromosome from their father, which does not carry the normal allele. Conversely, daughters will not be affected because they inherit one normal X chromosome from their father. However, there is a 50 percent chance that a daughter will be a carrier of the X-linked recessive trait like her mother, given that daughters receive one of their X chromosomes from their mother. Examples of X-linked recessive disorders include color blindness, hemophilia, and some forms of muscular dystrophy. These conditions are more common in males because they have only one X chromosome, and the presence of a single recessive gene on the X chromosome will result in the male being affected.
Son:
If the father is unaffected (XY), the son will inherit the X chromosome from the mother. In this case, there is a 0% probability that the son will be affected because he receives a healthy X chromosome from the mother.
If the father is affected (X-linked recessive, XrY), the son will inherit the affected X chromosome from the mother and the Y chromosome from the father. In this case, there is a 50% probability that the son will be affected.
Daughter:
If the father is unaffected (XY), the daughter will inherit the X chromosome from the mother. In this case, there is a 0% probability that the daughter will be affected because she receives a healthy X chromosome from the mother.
If the father is affected (XrY), the daughter will inherit the affected X chromosome from the mother and the X chromosome from the father. In this case, there is a 100% probability that the daughter will be a carrier of the X-linked recessive trait but not affected herself.