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Q.
A pedigree is shown below for a disease that is autosomal dominant. What would be the genetic make up of the first generation ?
Principles of Inheritance and Variation
Solution:
As the disease is autosomal dominant hence, the male parent who is normal must have the homozygous recessive genotype i.e., $aa$. The affected female can have either $Aa$ or $AA$ genotype. If the genotype is $AA$, all the progenies will surely be diseased but if the genotype is $Aa$ there is $50\%$ chance of having normal offsprings. But unfortunately the couple has produced only affected progeny and each of them must have the genotype $Aa$.
