12

A woman with hemophilia and a man without hemophilia get married. What are the chances that their first child will have hemophilia?

75 percent

50 percent

25 percent

100 percent

50 percent

Explanation:

Hemophilia is a disorder in which blood doesn't clot normally.

Lets consider Xn as hemophilia gene.

So woman affected with hemophilia will have XnXn gene and man not affected with hemophilia will have XY gene.

When they both undergo crossover, genes in child will be XXn (girl - carrier), XXn (girl - carrier), XnY (boy-affected) and XnY (boy-affected).

Parent Gene:

XnXn (affected woman)

XY (Man not affected)

After crossing over - children gene for first generation:

XXn (girl-carrier) XXn (girl-carrier) XnY (boy - affected) XnY (boy - affected)

Hemophilia is a X - linked recessive disease which means women are only carrier for this disease untill or unless both the X genes are hemophilia gene and man have more chances to get affected as they have only one X - linked gene.

It means 2 out 4 children are affected.

So, there are 50 percet chances that their first child will have hemophilia.