Question

1. A female who does not carry the hemophilia gene and a male hemophiliac (he has made it to his reproductive years thanks to recombinant DNA technology that has produced clotting factor for him) produce four children. Their four children (two of each sex) have normal clotting blood. One of the daughters marries a non-hemophiliac male and has three non-hem offspring (two males and one female). The other daughter of generation II marries a hemophiliac male and they have one male hemophiliac child and one female hemophiliac child. At this date, none of the male children produced by generation I have had any offspring. Construct/Draw a pedigree of the three generations for this family.    Write the genotype of each individual in this pedigree next to its symbol. Indicate those individuals for which the exact genotype cannot be determined.

Answer 1

Haemophilia is a x- linked recessive disease and the gene for this disease is present on X chromosome. For a female to be affected both the X chromosome should be affected and for a male to be affected only one X chromosome should be affected as it has only one copy of X. When only one X chromosome is affected in a female it is said to be carrier of the disease.

The pedigree for the three generations are drawn below:- The genotype of the female of the third generation cannot be determined.