Incomplete Dominance and Codominance

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Snap Dragons

• Both the red and white pigments are expressed
• We see a blended trait
• Neither one is dominant

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Incomplete Dominance

One trait is not completely dominant over the other. This produces a new phenotype that is a blend of the other two.

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Incomplete Dominance

• Let C represent the trait of flower colour
• Since there are two traits that are both dominant, we will use a superscript to indicate the dominant alleles of the same trait

C

C

R

W

red allele

white allele

red genotype

white

genotype

pink genotype

(homozygous)

(homozygous)

(heterozygous)

P: C^R C^R x C^W C^W

C^R

C^R

C^W

C^W

C^R C^W

C^R C^W

C^R C^W

C^R C^W

Codominance

• The heterozygous genotype results in both alleles being expressed and are individually visible.
• This does not produce a third blended phenotype, but rather a clear display of both traits