Exceptions to Mendel’s laws

1) Incomplete dominance Some alleles are not completely dominant and the offspring will have a “blending” of the parents traits. EX: Red flower x White flower  Pink flowers

Incomplete dominance

2) Codominance 2 alleles are equally dominant and both are expressed in the offspring. EX: Roan horses and cows really have white & red hair (they appear brownish). Both hair colors show up when a white horse is bred to a “red” horse.

Codominance

3) Multiple Allele Traits A trait that has more than just 2 types of alleles. EX: human blood types** (also show codominance)

Multiple allele traits

4) Polygenic Traits A trait that is controlled by more than 1 gene. EX: human skin color, height, and eye color

5) Sex linked traits (X-linked) Some traits are found on the sex chromosomes instead of autosomes and are more likely to show up in one gender. EX: colorblindness & hemophilia **these traits generally affect males more than females.