Incomplete Dominance:

Incomplete dominance is a genetic concept that occurs when the phenotype of a heterozygous individual is an intermediate blend of the phenotypes of the two homozygous parents. In this inheritance pattern, neither allele is completely dominant over the other, resulting in a unique phenotype that is different from both parents. The alleles are said to be incompletely dominant or co-dominant.

Example:

One classic example of incomplete dominance is the inheritance of flower color in snapdragons (Antirrhinum majus). The gene responsible for flower color has two alleles: the red allele (R) and the white allele (W). When a homozygous red-flowered plant (RR) is crossed with a homozygous white-flowered plant (WW), the resulting heterozygous offspring (RW) exhibit a pink phenotype.

Explanation:

1. Genotypes:
- Red-flowered plant: RR (homozygous dominant)
- White-flowered plant: WW (homozygous recessive)
- Pink-flowered plant: RW (heterozygous)

2. Phenotypes:
- Homozygous red-flowered plants (RR) have red flowers.
- Homozygous white-flowered plants (WW) have white flowers.
- Heterozygous pink-flowered plants (RW) have pink flowers.

3. Blending Phenotype:
In incomplete dominance, the phenotype of the heterozygous individual is a blend or intermediate between the phenotypes of the homozygous parents. In the case of snapdragons, the red and white alleles do not exhibit complete dominance over each other. Instead, they blend to produce the pink phenotype in the heterozygous individuals.

4. Genetic Explanation:
The incomplete dominance in snapdragons occurs because the red pigment and the absence of pigment (white) mix together to produce a new pigment, resulting in pink flowers. This blending occurs at the molecular level, where the red pigment is not fully produced due to the presence of the white allele.

5. Punnett Square:
A Punnett square can be used to predict the genotypes and phenotypes of the offspring in incomplete dominance. For the cross between a red-flowered plant (RR) and a white-flowered plant (WW), the resulting offspring will be heterozygous (RW) with a pink phenotype.

Overall, incomplete dominance is a genetic phenomenon where neither allele is fully dominant or recessive, resulting in an intermediate phenotype in heterozygous individuals. The blending of traits at the molecular level gives rise to unique characteristics, as seen in the example of snapdragon flower color inheritance.