For Some Rare Autosomal Dominant Diseases, It Is Possible That

For some rare autosomal dominant diseases, it is possible that the dominant homozygote has never been seen. One reason is that the fetus with this genotype may die early in development and be spontaneously aborted. In fact, roughly 25% of all women will have a pregnancy end in spontaneous abortion at some point during their lifetimes. Consider a situation in which
Q/Q dies as an early fetus; Q/q lives to reproduce but is unaffected; q/q lives and is unaffected. What genotypes are possible among live-born children of the mating Q/q × Q/q? (Hint: Construct a 2-by-2 table to reflect the genotypes of the parents.)

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