Question

If mother is colour blind and father is normal then what will be the percentage of colour blind child (male and female ) in F1 progeny?

plz answer the problem of X -linked recessive trait

Answer 1

Assuming that colour blindness is the recessive trait, 100% of the males will be color blind, and 0% of the females will be.

Explanation:

Since the F1 progeny refer to the direct descendants:

Let `N` denote a dominant allele, and `n` a recessive allele.

If the father is normal, he has genotype `X^NY`.
If the mother is colour blind, she is homozygous recessive, with genotype `X^nX^n`.

Thus, all male children will inherit the `Y` chromosome from the father and the recessive `X^n` allele (colour blindness) from the mother. Thus they will all be colour blind.

On the other hand, all female children will inherit the dominant `X^N` allele from the father, thus making them `X^NX^n`, heterozygous normal (carriers). Thus, they themselves will not be colour blind, but they do have a chance of passing down the trait for colour blindness, i.e. having children who are colour blind.

Fancy words used:
Allele = version of a gene
Homozygous = both copies of the gene are the same, e.g. `X^nX^n`
Heterozygous = the two copies are different, e.g. `X^NX^n`