Here's a breakdown:
* Traditional Dominance: One allele completely masks the other. For example, in pea plants, the allele for purple flowers (P) is dominant over the allele for white flowers (p). A plant with Pp genotype will have purple flowers.
* Incomplete Dominance: Neither allele fully masks the other. Instead, the heterozygous genotype produces a phenotype that's a mix of the two homozygous phenotypes.
Example:
Imagine a flower with alleles for red (R) and white (W) petals.
* RR: Red petals
* WW: White petals
* RW: Pink petals (the blend of red and white)
Key Characteristics of Incomplete Dominance:
* No "masking": Both alleles contribute to the phenotype.
* Intermediate phenotype: The heterozygote displays a phenotype that is in between the two homozygous phenotypes.
* Phenotypic ratio: In a cross between two heterozygotes, the phenotypic ratio is 1:2:1 (one homozygous dominant, two heterozygous, one homozygous recessive).
Examples of Incomplete Dominance in Nature:
* Snapdragon flowers: Red flowers crossed with white flowers produce pink flowers.
* Human hair color: In some cases, a parent with dark hair and a parent with light hair can have a child with intermediate hair color.
* Sickle Cell Anemia: Individuals with one copy of the sickle cell gene have a milder form of the disease called sickle cell trait.
In summary: Incomplete dominance is a fascinating phenomenon where neither allele fully dominates the other, leading to a blending of traits in the offspring.
