12.4 Beyond Medelian Heredity I. Patterns of Heredity Can Be Complicated A. Incomplete Dominance 1. an individual displays a trait that is between the two parents a. example- flower color in snapdragons, a cross between red and white flowers produces pink color B. Codominance 1. two dominant alleles are expressed at the same time 2. different from incomplete dominance in that both traits are displayed a. example- roan hair color in horses, a cross between red and white hair results in a mix of both hair on the horse

C. Multiple Alleles 1. traits with more than two alleles a. example- human blood type – A, B, O 1. A & B are dominant over O 2. Neither is dominant over the other when both are present they are codominant D. Sex-Linked Traits 1. determined by genes only found on X chromosome 2. Sex linked disorders occur in men more than women a. ex.- being colorblind

1. weather conditions can affect phenotype E. Environmental Influences 1. weather conditions can affect phenotype a. the artic fox’s coat is red in summer and white in winter 1. the color pigments shut down due to the extreme cold. F. Polygenic Inheritance 1. Polygenic characters a. when several genes affect a characteristic b. ex.- eye color 2. maybe on same chromosome or many chromosomes 3. Linked – genes that are close together & help to determine the same trait