Thread: Pedigree 2

So, I have another problem with a pedigree. There is an autosomal recessive trait in a family. Father - AA, mother Aa, they have two children one of them is Aa (it is possible) but the other one is aa. And that´s the problem because she cannot inherit a from her father since he is AA. What could be the possible cause of that?? How can it be explained?? (the woman did not sleep with the postman ;P)

A rare and unusual event.

It is theoretically possible that the 'A' gene from the father mutated into the 'a' gene. (Only the one inside the fertilising sperm). After all, recessive genes (usually harmful) do arise in this way from time to time in the human population. This is how the gene for hemophilia arises, for example.