1. Beyond Mendel

2. Incomplete Dominance Neither allele is completely dominant
Heterozygous is a new phenotype, a hybrid, blending
Ex.
Red snapdragon (RR) is crossed with a white snapdragon (rr) yields all pink snapdragons (Rr)

3. Codominance
Where 2 alleles each affect the phonotype in separate ways.
When presented together, both appear
Ex. Blood types (AB), Roan horses (red and white hair)

4. Multiple Alleles
When genes exist in more than 2 allelic forms rather than in complete dominance where it was either dominant (D) or recessive (d)
Ex. Blood types A, B, O

5. Pleiotropy When genes affect more than one phenotypic character
Ex. If you have cystic fibrosis, the one gene affects respiratory and digestive parts of your body.

6. Epistasis
Two or more genes are involved in determining a particular phenotype.
Phenotypic expression of a gene at one locus alters that of a gene at a second locus.
Ex. Labrador retrievers (Labs)
Black coat dom to brown
Genotype is chocolate
Second gene determines if pigment
will be deposited in hair (ee) yellow

7. Polygenic inheritance
Effect of two or genes on a single phenotypic character.
Ex. Skin coloration – 3 genes (A, B and C) AABBCC or aabbcc
Cumulative effect, usually results in bell curve
Height, eye color