1. Ch. 10.3: Exceptions to Mendel’s Rules of Inheritance Objectives: 1.Describe how alleles interact in intermediate inheritance. 2.Describe inheritance patterns involving multiple alleles. 3.Describe how polygenic inheritance can result in a wide range of phenotypes. 4.Describe how environmental conditions can affect phenotype expression. Vocabulary: Intermediate inheritance Codominance Polygenic inheritance

2. Intermediate Inheritance Incomplete Dominance Heterozygotes have a phenotype that is intermediate b/w dominant & recessive. Example P1: Red x White flowers F1: Pink flowers F2: 1 red: 2 pink: 1 white

3. Intermediate Inheritance Traits from both alleles appear to blend.

4. Multiple Alleles More than 2 alleles for an inherited character. Eye color Blood type: A, B, AB, or O Fur color

5. Codominance Both alleles are expressed in heterozygotes. Not incomplete dominance BOTH traits are expressed. Blood type: AB has antigens A and B on the surface. Alleles written as superscripts: I A, I B, I AB, ii

6. Blood Type: Codominance & Multiple Alleles

7. Polygenic Inheritance Multiple genes affect a trait. Each gene has alleles that contribute. Range of variety in traits Examples: Height Skin color

8. Polygenic Inheritance

9. Environment influences gene expression Temperature, pressure, pH, presence of certain chemical compounds influence how genes are expressed. Epigenetics: study of how genes are influenced by environmental conditions.