Question

Compared the Mendelian Dominance, how to incomplete dominance and codominance increase the number of phenotypes? Provide an example of each to illustrate your point.

Answer 1

Answer/Explanation:

Incomplete dominance

In incomplete dominance, one allele is not entirely dominant over the other, so heterozygotes (organisms with two different alleles for the gene) show an intermediate or blended phenotype.

For example, consider flower colour.

• If the allele for red flowers (R) was dominant over the allele for white flowers (r), then there are three possible genotypes (RR, Rr, and rr) and two possible phenotypes. (Red (RR and Rr) and white (rr)).
• However, if the allele for red flowers (R) was incompletely dominant over the allele for white flowers (r), then there are three possible genotypes (RR, Rr, rr), and three possible phenotypes (red (RR), white (rr), and pink (Rr))

Co-dominance

In incomplete dominance, two alleles are both expressed, one is not dominant over the other. Therefore, heterozygotes (organisms with two different alleles for the gene) express both traits.

For example, consider flower patterns.

• If the allele for spots (F) was dominant over the allele for stripes (f), then there are three possible genotypes (FF, Ff, and ff) and two possible phenotypes. (Spots (Ff and ff) and stripes (ff)).
• However, if the allele for spots (F) was co-dominant to the allele for stripes (f), then there are three possible genotypes (FF, Ff, ff), and three possible phenotypes (spots (FF), stripes (ff), and spots and stripes (Ff))