Question

Which one of the following will not be possible if the allele for dark-colored hair is dominant over the allele for light-coloured hair?

• A. A light-haired couple produces a baby with dark hair.
• B. A dark-haired couple produces a baby with light hair.
• C. A light-haired woman and a dark-haired man produce a light-haired baby.
• D. A dark-haired woman and a light-haired man produce a light-haired baby.
• E. A dark-haired woman and a light-haired man produce a dark-haired baby.

Answer 1

The correct option is A A light-haired couple produces a baby with dark hair.

Since dark coloured hair is dominant over allele of light coloured one, two light coloured hair individuals (dd x dd) can not give a offspring with dark coloured hair (DD or Dd). Option B is incorrect as a dark-haired couple produces a baby with light hair if both parents are heterozygous dominant (Dd x Dd). Option C is incorrect as a light-haired woman (dd) and a dark-haired man produces a light-haired baby if the man is heterozygous dominant (Dd). Option D is incorrect as a dark-haired woman and a light-haired man produces a light-haired baby if the woman is heterozygous dominant (Dd). Option E is incorrect as a dark-haired woman (DD) and a light-haired (dd) man produce a dark-haired baby (Dd).