Complex Methods of Inheritance

Incomplete Dominance No gene is completely dominant resulting in a third phenotype. The third phenotype is usually a mixture of the dominant and recessive trait Example: Pink snap dragon

Codominance Both alleles are dominant, therefore both traits are visible resulting in a third, mixed phenotype Example: Speckled Chicken

Sex Linked Alleles are found on either the X or Y chromosome. Examples: Colorblindness, Ricketts, and Hemophillia in Humans – Calico cats – Eye color in fruit flies

Multiple Alleles One allele codes for more than one trait Example Blood types

Polygenic Inheritance Expressed traits are carried more than one gene Example: Hair color, Height, Skin Color

Epistasis The trait is influenced by other alleles If a dominant B is present, then the mouse will be black unless there is a homzygous c then the mouse will be white. Two homozygous recessive b’s with a dominant C trait yield a brown coated mouse.