1. Polygenic Traits: Co-dominance & Incomplete dominance

2. Despite Mendel’s work in genetics, there always seems to be exceptions. - Not all genes show simple patterns of dominant & recessive - Some traits are controlled by more than 1 gene or allele.

3. Polygenic Trait - Where several genes or alleles control a trait. They can be on the same chromosomes, or even on different numbered chromosomes. Chromosome Pair #3 Chromosome Pair #7 Chromosome Pair #12 All 3 alleles control a trait like hair color..

4. Another exception is Called.

5. Co-dominant – Where two dominant alleles are expressed at the same time. A great example of this is Blood Type.

6. Blood type in genetics is shown with the letter “I” with a “A” or “B” attached to it. “A” blood type = “B” blood type = “AB” blood type = “O” blood type = I A I A or I A i I B I B or I B i IAIBIAIB ii A & B type blood can either be homozygous or heterozygous. I = dominant ; i = recessive

7. Before DNA testing, blood testing was primarily used to determine if a father sired the baby. (Paternal Test) Blood types are used in simple punnett squares. If the father has A type blood (I A I A ) and the mother has B type blood (I B i) what are the possible blood types of the baby? IAIA IAIA IBIB i IAIBIAIB IAIBIAIB IAiIAi IAiIAi

8. The baby has O type blood and the mom has B type blood. She claims the father has A type blood. Is this possible? Baby genotype = Mom = Dad = IBIB IAIA i i ii So yes, it is possible… ii I B I B or I B i I A I A or I A i

9. There are 5 children in this family… Child #1 has AB type blood Child #2 has B type blood Child #3 has O type blood Child #4 has O type blood Child #5 has A type blood Can these 5 children come from the same parents? Use a punnett square to prove your answer!

10. #1 – AB = I A I B #2 – B = I B I B or I B i #3 – O = ii #4 – O = ii #5 – A = I A I A or I A i Children’s Blood Type What is Parent 1 Blood Type? What is Parent 2 Blood Type? IAIA i IBIB i IAIBIAIB IBiIBi IAiIAi ii

11. INCOMPLETE DOMINANCE Is another exception to Mendel’s rules. This is shown a lot in flowers.

12. (definition) Incomplete dominance – Where an individual displays a trait that is intermediate between the two parents. X = Red Blue Purple

13. Let’s see this on a Punnett Square R = Red flower, B = blue flower, BR = purple Cross a pureblood Red flower with a pureblood blue flower. RR B B BR Now cross 2 of the purple together to see what you get!

14. R = Red flower, B = blue flower, BR = purple RB R B RR BR BB 25% will be Red 50% will be Purple 25% will be Blue

15. VOCABULARY ! Polygenic Trait Co-dominant Blood type examples Incomplete dominance