question_answer

A couple whose sons are color blind with AB blood group, identify the parents from the following:

A)  Mother color blind with A blood group; and father normal with blood group B

B)  Mother normal with blood group A, and Father color blind with blood group B

C)  Mother color blind with blood group B, and Father normal with blood group B

D)  Mother normal with blood group A, and Father color blind with blood group B.

Correct Answer: B

Solution :

                 Color blindness is caused by recessive sex-linked gene carried by X chromosome. So, in male, one recessive gene is sufficient for its expression i.e., \[({{X}^{C}}Y)\]but female needs two recessive genes \[({{X}^{C}}{{X}^{C}})\] for the expression of color blindness. Mother will colorblind with A blood group and father normal with blood group B