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

1 Answer
Feb 6, 2018

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#