Question

If a father and son are both defective in red-green colour vision, is it likely that the son inherited the trait from his father? Comment.

Answer 1

Red-green colorblindness

Red-green colour blindness is a sex-linked recessive disease. It causes inability to distinguish between red and green colours by human eyes.

Pedigree analysis, if the father is colourbind

Pedigree analysis shows the below mentioned pattern, if the father is colourbind and the mother is normal.

Gene for colour blindness is present on X - chromosome. Thus, sons only receive it from their mother, not from their father.

Pedigree analysis, if the mother is a carrier

Pedigree analysis shows the below mentioned pattern if the mother is a carrier and father is colour blind.

Son does not inherit the red-green colour blindness from his father

If a father and son are both defective in red-green colour vision, then it can be inferred that the color blind trait has beeen inherited by the son from his mother because the gene for colour blindness is located on the X chromosome. A son inherits X chromosome from his mother. A colour blind mother or carrier mother must have transmitted the trait to her son.