Color blindness is a recessive trait linked to the X chromosome. In a family where the mother has a normal color sensation, a color blind daughter was born. Set the genotypes of the parents. What is the probability of having a healthy son?
We introduce the notation of genes:
A – normal color perception (norm);
and – color blindness.
– Determine the genotypes of the parents. A color blind daughter, her genotype XaXa, was born in this family. It is known that a child inherits one of the allelic genes from the mother, and the other from the father. Therefore, the genotype of a mother with normal color sensation is XAXa, i.e. she is a carrier of color blindness. The father’s genotype is XaY, he is color blind.
Thus, the probability of having a healthy son in this family is 25%.
Answer: the probability of having a healthy son is 25%.
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