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A woman is phenotypically normal, but her father had the sex-linked recessive condition of red-green colorblindness. If she has children with a man with normal vision, what is the probability that their first child will have normal vision and their second child will be colorblind

User Glaucon
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Final answer:

The probability of a female carrier of red-green colorblindness and a normal male having children with colorblindness is 0% for daughters and 50% for each son they have. Each child's inheritance is an independent event.

Step-by-step explanation:

The question is about red-green colorblindness, which is a sex-linked recessive condition. Since the woman's father had the condition, it means the woman is a carrier of the colorblindness allele but does not express the condition because it is recessive and she has only one copy. Red-green colorblindness is more common in males because they have only one X chromosome. If a male inherits the X chromosome carrying the allele for colorblindness from his carrier mother, he will be colorblind.

Regarding the probability of her children with a man of normal vision: their first child will have a 50% chance of being colorblind if the child is male, and a 0% chance if the child is female (since the father provides a normal X chromosome). For the second child, the probabilities remain the same—50% for a male and 0% for a female, because the inheritance of each child is an independent event.

It should be noted that the condition can only be passed to a son from a mother who is a carrier, and not from the father as the father passes the Y chromosome to his sons. A female would have to inherit two colorblindness alleles to express the condition, which would only occur if her father was colorblind and her mother was either a carrier or colorblind herself.

User Joshua Owoyemi
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