Incomplete Dominance

Polymorphic

Different combinations of alleles produce more than 2 phenotypes

What is the molecular basis behind complete and incomplete dominance?

Dominant allele (gene) encodes for a protein that leads to a prevalent phenotype. Recessive allele (gene) have been altered in such a way that they no longer encode for the protein. This is true of many (but not all) dominant alleles in a complete dominance relationship

Codominance

Heterozygotes have phenotypes of both inherited alleles. Each allele contributes to produce a multi-part phenotype. Typically involving structural proteins; both types expressed by single cell

Environmental effects on phenotype

In addition to genes, phenotypes are controlled by interplay with environment. Genes provide blueprint, environment provide nutrients and proper conditions so that plan can be executed

Multiple alleles

Many genes have three or more variants, but two will be inherited in diploid individuals

Incomplete dominance

Neither allele is dominant, so phenotype is intermediate. (Ex: Skin color, height, voice pitch, hand size, hair texture)

Incomplete dominance Note

Note alleles for traits that lead to incomplete dominance are designated differently. There is no dominant, capital C, or recessive, lower case C. Rather, the trait is designated C and then superscripts are used to differentiate the trait (R for red, W for white).

Norm of reaction

phenotypic range that individuals with a particular genotype exhibit under differing environmental conditions