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.
No, defective gene for red-green colour vision cannot be inherited from father to his son. Gene for colour blindness is X-chromosome linked and sons receive their sole X-chromosome from their mother, not from their father. Male to male inheritances is not possible for X-linked traits in humans.
In the given case, the mother of the son must be a carrier (heterozygous) for colour blindness gene, thus transmitting the gene to her son.