Beyond Mendel - Genetics

Incomplete Dominance


Other Examples of Incomplete Dominance

Sickle cell disease in humans.

AA x aa = Aa (sickle cell trait), where some blood cells will have abnormal shapes

Carriers (Aa) can have a child with sickle cell disease (1/4)

punnett square





blood dropletBlood Types - Multiple Alleles and Codominance

blood types

When doing blood type crosses, you will need to know whether at type A or B person is heterozygous or homozygous. Type O's are automatically OO and type AB is automatically AB. Crosses are performed the same as any other.

punnett square

Multiple Allele Traits and Epistasis

In labrador retrievers, coat color is determined by one gene with four different alleles.

Black (B) is dominant to brown (b)
The yellow coat color (ee) is epistatic. When it both (ee) are present the coat will be yellow

labrador punnett

Polygenic Traits

Environment and Phenotype