Mendelian inheritance patterns can be more complex than simple dominant and recessive traits. There are several exceptions including incomplete dominance where a blending phenotype results from heterozygotes, codominance where both alleles are fully expressed simultaneously in heterozygotes producing a third phenotype, multiple alleles where more than two alleles exist for a single trait, and polygenic traits which are influenced by two or more interacting genes resulting in a continuous variation of phenotypes.

1. Mendelian Exceptions Chapter 11 Section 3

4. Independent Assortment in Peas __ Round yellow __ Round green __ Wrinkled yellow __ Wrinkled green 9 3 3 1