A normal woman whose father was colourblind is married to a normal man, (assuming equal distribution of female gametes), then _________.

Question

Quantrex Academy · Accepted Answer

Correct answer: A. 50\% of their sons will be colourblind.

Colour blindness is an X-linked recessive trait.

Let

X^C

be the normal allele and

X^c

be the allele for colour blindness.

The woman's father was colourblind (X^c Y

), so he passed the

X^c

chromosome to her. Since she is normal, her genotype is

X^C X^c

(carrier).<br><br>The normal man has the genotype

X^C Y

.<br><br>A cross between the carrier woman (X^C X^c

) and the normal man (X^C Y

) produces the following offspring:<br><br>Daughters:

X^C X^C

(normal)

and X^C X^c

(normal carrier).<br><br>Sons:

X^C Y

(normal)

and X^c Y

(colourblind).<br><br>Since the sons receive their X chromosome from the mother, who produces

X^C

and

X^c

gametes in equal proportions, 50\%

of the sons will be normal and

50\%

will be colourblind.

Answer:

50\%

of their sons will be colourblind.

A normal woman whose father was colourblind is married to a normal...