Question

How can a person be normal for a trait even when carrying one defective gene for that trait?

Answer 1

Answer:

A person can be normal for a particular diseased trait, showing no complexities or irregularities because of dominance of the normal allele over the abnormal one.

A person carries a pair of sex chromosome received from each parents. So, the chances of expressing the diseased trait becomes low , if that person has one parent who is recessive for the affected trait and another parent having unaffected dominant trait.

The defected allele gets suppressed as a carrier and the dominant normal allele from the unaffected parent gets expressed.