This one is for you assume that this pedigree shows the inh

This one is for you - assume that this pedigree shows the inheritance of a rare autosomal condition. Note that the father (II-4) is a known carrier and that this couple has had 3 normal children. What is the probability that she is a carrier?

Solution

The disease is rare autosomal. In other words it is autosomal recessive disorder. Now the male and female in II-1 and II-2 have disease. Lets call their genotype as \"aa\". But Their parents in I generation are normal. This means they are carriers of the disease with genotype Aa and Aa. Their third daughter II-3 has no disease, Her genotype can be Aa or AA, so probability to carry a recessive allee a is 1/2. If she had had a diseased child, her genotype would have been Aa with 100%probability. But as has all healthy kids, probability of her being carrier is 1/2.