1. Polygenic Traits

2. Definition zSome traits are determined by the combined effect of two or more pairs of alleles. These traits are called polygenic traits. zEach pair of alleles adds something to the resulting phenotype. zOther names for polygenic traits are multi- factorial traits, or quantitative traits.

3. Polygenic traits are continuous zBecause so many alleles contribute to the final phenotype, a variety of phenotypes can occur! zFor example, height is a polygenic trait.

4. Polygenic Traits are Continuos zWhen dealing with polygenic traits that are only controlled by two pairs of alleles, we can complete Punnett squares to determine the genotypes and phenotypes of the F1 generation.

5. Examples of Polygenic Traits zPepper Color Gene 1: R=red r=yellow Gene 2: Y=absence of chlorophyll (no green) y=presence of chlorophyll (green)

6. Pepper Color zPossible genotypes: zR-/Y- : red (red/no chlorophyll) zR-/yy : brown/orange (red/chlorophyll) zrr/Y- : yellow (yellow/no chlorophyll) zrr/yy : green (yellow/chlorophyll)

7. Pepper Color zTry crossing a brown pepper (RRyy) with a yellow pepper (rrYY). zWhich trait will your offspring (F1 generation) produce? zWhat traits are produced when you cross two of the peppers found in the F1 generation?

9. More Polygenic Traits zChicken Combs: yThere are 4 different comb shapes that can appear in a chicken. yComb shape is controlled by two genes found on two different pairs of chromosomes. xGene 1: R xGene 2: P

10. Chicken Comb Example: z4 different phenotypes result: zRose Combs (R-pp) zWalnut Combs (R-P-) zPea Combs (rrP-) zSingle Combs (rrpp)

11. Try these questions: zIndicate the phenotypes of the parents and give the genotypic and phenotypic ratios of their offspring for the following crosses: (Refer to your phenotype chart for chickens) zrrPP x RRpp zRrPp x RrPp

12. Another example of a polygenic trait: zHair Color yHair color is controlled by alleles on chromosomes 3, 6, 10, and 18. yThe more dominant alleles that appear in the genotype, the darker the hair!

13. Polygenics Problem zThe height of plants is controlled by 4 pairs of alleles. Alleles A, B, and C contribute 3 cm to the plant's height. Alleles that are recessive do not contribute to the height. Gene L is always found in a homozygous dominant condition and always contributes 40 cm to the height. za) What would be the height of a plant with the genotype AABBCCLL? zb) What would be the height of a plant with a genotype aabbccLL? zc) What would be the height of the offspring produced from a cross between the plants in a) and b)? zd) What would be the heights of the offspring produced from a cross between AaBbCcLL and AaBbCcLL? (now there is a challenge!)

14. Let’s Review: zSex linked traits z- X linked recessive z- X linked dominant z- y linked zSex influenced traits zPolygenics zEpistasis zPick up a piece of flip chart paper and a marker for your table. Summarize the new genetics topics.