Answer:
B/2. An allele that is only expressed when no dominant allele is present.
Explanation:
Alleles always come in pairs, and we represent them with letters. Uppercase letters represent dominant alleles, and recessive alleles are represent by lowercase letters.
A recessive trait can only appear when the pair of alleles contains 2 lowercase letters, otherwise, if there are 2 uppercase letters or 1 of each, a dominant trait will be seen.
So:
AA - a pair of 2 dominant alleles (here we get a dominant trait).
Aa - a pair of 1 dominant and 1 recessive allele (here we get a dominant trait)
aa - a pair of 2 recessive alleles (here we get a recessive trait).
→ As we can see, we only get a recessive trait when there is a pair of 2 recessive alleles, therefore no dominant alleles in the pair.
Hope it helped,
BiologiaMgaister
