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Title: A man with hemophilia (a recessive, sex-linked condition) has a daughter of normal phenotype. She ... Post by: Biologylover200 on Dec 28, 2016 A man with hemophilia (a recessive, sex-linked condition) has a daughter of normal phenotype. She marries a man who is normal for the trait. What is the probability that a daughter of this mating will have hemophilia? That a son will have hemo- philia? If the couple has four sons, what is the probability that all four will be born with hemophilia?
Title: Re: A man with hemophilia (a recessive, sex-linked condition) has a daughter of normal phenotype. ... Post by: akorne on Feb 16, 2017 The man is X*Y where his X-chromosome carries the mutation. He shows the phenotype as he has no back-up good copy of the affected gene.
His daughter inherits the affected X-chromosome from her father and I assume a normal X-chromosome from her mother so she X*X. Since she has a back up good copy of the gene on her unaffected X-chromosome she is phenotypically normal. She marries a man who is normal, XY. Any daughters produced from this mating will have at least one normal X (from the father) so will be phenotypically normal i.e. 0% chance of having haemophillia. Any sons produced from this mating have a 50% chance of inheriting the affected X-chromosome from the mother i.e. 50% chance of haemophillia for any son. For all 4 sons: (50%)^4 = 6.25% |