Monohybrid Monohybrid crosscross

Incomplete dominanceIncomplete dominance

Incomplete dominanceIncomplete dominance

A kind of A kind of dominancedominance occurring in occurring in heterozygotesheterozygotes in which the in which the dominantdominant genegene or allele is only partially or allele is only partially expressed, and usually resulting in expressed, and usually resulting in an offspring with an intermediate an offspring with an intermediate phenotype. phenotype.

Source: Source: http://www.biology-online.org/dictionary/Incomplete_dominancehttp://www.biology-online.org/dictionary/Incomplete_dominance

Example: Color in Example: Color in SnapdragonsSnapdragons

Red snapdragons Red snapdragons result from result from homozygous homozygous dominant RRdominant RR

White snapdragons White snapdragons result from result from homozygous homozygous recessive rrrecessive rr

Pink snapdragons Pink snapdragons result from result from heterozygous Rrheterozygous Rr

Alleles

R rRr

Rr X Rr

Alleles

R rR RR Rrr Rr Rr

Rr X Rr

Genotypic outcomesGenotypic outcomes

3 possible combinations3 possible combinations 1 RR homozygous dominant1 RR homozygous dominant 2 Rr heterozygous 2 Rr heterozygous 1 rr homozygous recessive1 rr homozygous recessive Genotypic ratio = 1:2:1Genotypic ratio = 1:2:1

Phenotypic outcomesPhenotypic outcomes

1 RR red snapdragons1 RR red snapdragons 2 Rr pink snapdragons2 Rr pink snapdragons 1 rr white snapdragons1 rr white snapdragons Phenotypic ratio = 1:2:1Phenotypic ratio = 1:2:1