question_answer

                A woman with two genes (one on each 'X' chromosome) for haemophilia and one gene for colour blindness on the 'X? chromosomes marriesa normalman. How will the progeny be?                                             

A)              All sons and daughters haemophilic and colourblind

B)              Haemophilic and colourblind daughters

C)              50% haemophilic colourblind sons and 50% haemophilic sons

D)              50% haemophilic daughters and 50% colourblind daughters

Correct Answer: C

Solution :

                Haemophilia and colour blindness both are recessive X-linked traits. They express in males when present in single copy (heterozygous) but in females they express only when present in homozygous condition.                                 Results:  50% sons are colourblinds and haemophilic.                  50% sons are haemophilic only.                  50% daughter are carrier for colour blindness and haemophilia.               50% daughter are carrier for haemophilia only.