1. Complex Patterns of Inheritance Exceptions to Mendel’s rules: not simple dominant/recessive inheritance

2. Incomplete Dominance The phenotype of the heterozygote is INTERMEDIATE. Red + White = Pink

3. RR’ RR R’ R’ Red parent plant White parent plant All pink offspring!

4. CodominanceCodominanceCodominanceCodominance Both alleles are expressed! Red + White = Both Red and White (NOT pink!)

5. Pleiotropy The ability of a gene to affect an organism in many ways, not just in one way. Example: Human disease PKU (phenylketonuria) Causes mental retardation and reduced skin & hair pigmentation Caused by mutation in gene for creating the enzyme that breaks down the amino acid phenylalanine This mutation makes the person unable to break down phenylalanine, leading to toxic levels that can damage the body in many ways. PKU is manageable with medications and by following a diet free of phenylalanine.

6. PKU patient

7. Epistasis A gene at one location affects the expression of a gene at another location. Coat color in mice: BB & Bb (black) bb (brown) Gene that allows color to be deposited: CC & Cc (color is present) cc (albino)

8. Multiple Alleles and Codominance This is a gene that is controlled by more than two forms of an allele Blood Types: A, B, AB, O A and B are codominant O is recessive to both

9. Type A: I A I A or I A iType B: I B I B or I B i Type AB: I A I B Type O: ii

10. Polygenic Traits Trait controlled by two or more GENES (not alleles) AaBbCc x AaBbCc Skin Pigmentation Height

11. Sex-Linked Traits Humans have 46 chromosomes 22 pairs autosomes (pairs 1-22) 1 pair sex chromosomes (pair #23) Males: XYFemales: XX Sex-Linked traits are located on the X chromosome. These traits tend to affect males more than females. WHY?? Baldness

12. Colorblindness is a sex-linked trait. People with normal vision should see a light image of a red/brown sailboat.

14. Epigenetics