Question

How many possible genotypes and phenotypes are there for a single gene trait that shows dominance in any given population? A.One genotype, one phenotype
B.Two genotypes, two phenotypes C.Three genotypes, two phenotypes D.Two genotypes, three phenotypes

Answer 1

Let D be the dominant allele and d be the recessive allele. Possibilities:
DD (dominant phenotype)
Dd (dominant phenotype)
dd (recessive phenotype)

Therefore, there are three genotypes, two phenotypes.

The answer is C.

Answer 2

The answer is C.Three genotypes, two phenotypes.

Imagine gene for flower colors. Let A allele be dominant and a allele be recessive allele for the trait. A allele is responsible for red color and a allele for white color

The genotypes are:
1. AA
2. Aa
3. aa

However, there will be only two phenotypes:
1. red flowers
2. white flowers

This is because of the dominance of A allele over a allele. So, red flowers will have plants with genotypes AA and Aa while white flowers will have plants with genotype aa.