Answer: Option A
:
A
From the chart we can see that female parentis carrier for the disease. The male parent is unaffected. Let us denote the allele as 'F'. The mother's genotype will be Ff since she is a carrier. The father can be either FF or Ff. In the first generation, we see that none of the offsprings are affected. Out of five offsprings, three are carriers and two areunaffected. This indicates that the father's genotype is FF. This also tells us that the gene is recessive. If it was a dominant trait, it would have showed in the offsprings. Also, both male and female children are carriers, indicating that the trait is not sex linked. That means the pedigree chart shows a autosomal recessive disorder. In the second generation again, we see that in one family father is a carrier and mother is unaffected. For these parents one daughter is a carrier (Ff) and one daughter is unaffected (FF). From this we can make out that father is heterozygous (Ff) for the trait and the mother is homozygous dominant (FF). For the second family, we see that both mother and father are carriers, so both of them are heterozygous for the trait (Ff). Out of the five offsprings,two are carriers (one boy and one girl), two are affected (one boy and one girl) and one boy is unaffected. Thus, we can infer that the trait is autosomal recessive in nature.