Complex Patters of Inheritance

Kyla Luangkhot

Multiple Alleles

Traits are controlled by more than two alleles.

There are 3 possible phenotypes.

Ex) blood types ; A, B, AB, & O. There are 3 alleles for the gene that determines blood type.

Incomplete Dominance

Neither gene is expressed with another allele.

Offspring that are heterozygous is usually hybrid between the homozygous parents.

Ex) A red tulip & a white tulip are cross pollinated they result in a pink tulip, A red bird and blue bird mate and their offspring is purple.


Both alleles are completely expressed if 2 alleles have a codominance relationship.

Offspring that are heterozygous are equally expressed.

Ex) Person with type AB blood, both A and B allele are equally expressed, If a person has type A protein they have type A blood.

Polygenic Traits

Trait is controlled by 2 or more genes.

Phenotypes are not shown, though each of the genes contributing to the trait is inherited.

Ex) Height, skin color, eye color, & weight.