The daughter of a colour- blind father and a normal mother marries a normal male. What percentage of male children of this couple will be colour -blind ?

Question

Quantrex Academy · Accepted Answer

Correct answer: A. 50 %

Colour blindness is an X-linked recessive disorder.

Genotype of the colour-blind father:

X^c Y

Genotype of the normal mother:

X^C X^C

The daughter receives the

X^c

chromosome from her father and the

X^C

chromosome from her mother. Thus, her genotype is

X^C X^c

(carrier).

She marries a normal male, whose genotype is

X^C Y

.

The cross between the carrier female (X^C X^c

) and the normal male (X^C Y

) produces the following offspring:

Male children receive their X chromosome from the mother and Y chromosome from the father.

The mother produces two types of eggs:

X^C

and

X^c

in equal proportions.

Therefore, the male children will be

X^C Y

(normal)

and X^c Y

(colour-blind) in a

1:1

ratio.

Hence,

50\%

of the male children will be colour-blind.

Answer: 50 %

The daughter of a colour- blind father and a normal mother marries...

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