question_answer

            A marriage between normal-visioned man and colourblind woman will produce offspring:              

A)                                                                                                                                                                                        50% colourblind sons and 50% carrier daughters

B)             colourblind sons and carrier daughters

C)             normal males and carrier daughters

D)             colourblind sons and 50% carrier daughters

Correct Answer: B

Solution :

                Colourblindness is sex-linked recessive character carried by X chromosome. Since males have only one X chromosome (XY), presence of gene for colour blindness on X chromosome (X) would cause colour blindness while in woman both chromosomes should have the gene for colour blindness to appear. \[{{X}^{C}}X\] woman would be carriers for the disease. A cross between XY (normal man) and colour blind woman \[({{X}^{C}}{{X}^{C}})\] would produce all colour blind son and carrier daughter.                 Result of this cross is:                 1. Colourblind sons.             2. Carrier daughters.