Question

How do incomplete dominance and codominance increase the number of phenotypes?

Answer 1

Increase in phenotypes in incomplete dominance :

1. Incomplete dominance is the expression of genes partially.
2. It is the blending of characters in heterozygous conditions, where both the characters are partially expressed.
3. So instead of two phenotypes, we get three phenotypes with two alleles in case of complete dominance.
4. The variants or alleles are neither dominant nor recessive. In incomplete dominance, complete dominance is in a reduced ratio than in Mendel's experiments.
5. It is considered a dilution of the dominant allele and recessive allele.
6. Pink colors of flowers such as snapdragons, the shape of hairs, etc. are examples of incomplete dominance.
7. So apart from the dominant and recessive gene, a new gene showing intermediate characteristics is found in offspring.
8. Hence there is an increase in phenotype.

Increase in phenotypes in codominance:

1. Codominance is the expression of two versions of the same genes separately to give different traits to an individual.
2. When both alleles show dominance and both are expressed phenotypically.
3. Both the genes from parents are produced in equal amounts.
4. The most common example of codominance is seen in blood groups.
5. There will be a total of three phenotypes with two alleles. E.g. If alleles A and B are codominant then we get one homozygous for AA, one homozygous for BB, and one heterozygous, i.e. AB.
6. So apart from the dominant and recessive gene, a gene having both dominant characteristics is seen in offspring.
7. Hence there is an increase in phenotype.

Hence codominance and incomplete dominance increase the number of phenotypes.