Question

What are the consequences of marrying a normal woman to a normal man carrying a colour blindness gene ​

Answer 1

Answer:

Complete answer:

-If they marry a normal man then 50% of their grandson or 25% of grandchildren will become color-blind. This can easily be understood by the following cross. Therefore for the case of carrier daughters, only 25% of their children will be colorblind. Which also means 50% of grandsons will be colorblind.

Answer 2

Answer:

All the children will be normal.

Explanation:

Colourblind is a X-linked recessive disorder. Since, males are hemizygous for chromosome, one copy of the affected gene in each cell is sufficient to cause the disorder (X

c

Y). Females have two X chromosomes and hence need two copies of the affected gene to cause the disorder (X

c

X

c

). Females heterozygous (X

c

X) for this trait be normal but serve as a carrier of the disease. According to the question, the colour blind man marries a normal vision woman.

Parent generation : (XX) x X

c

Y

Gametes :

(X

c

Y) -->

XX X

c

Y

X X

c

X

carrier girl

XY

normal boy

X X

c

X

carrier girl

XY

normal boy

Thus, all children of a normal woman and colour blind man will be normal. Because father transmit its X-chromosome to the daughter and daughter need two copies of the affected alleles to express the disease. The wild type normal allele mask the effect of father's affected allele in daughter and they show normal phenotype. Sons receive their X-chromosome from mother who is normal here, hence no disease in them.