From the given problem, if we let A/a be the gene for sickle cell disease and the superscript b in the X chromosomes indicate the recessive colorblind allele, we can deduce that the man would have the genotype aaX+Y, while his wife would have the genotype AaXbXb.
A man homozygous for sickle cell disease (an autosomal recessive disease, i.e. not sex linked) who has normal vision marries a woman heterozygous for sickle cell disease who is colorblind (a recessive X-linked condition). What is the chance that a child (of either sex) born to them will have both sickle cell disease and be colorblind.
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