Complex Patterns of Inheritance: Incomplete Dominance vs. Codominance (5R)

1. Complex Patterns of Inheritance: Incomplete Dominance vs. Codominance(5R)

2. Review of Simple Mendelian Genetics • Law of Segregation: each gene has 2 different alleles that are separated when gametes form • 1 allele goes to 1 gamete and the other allele to a different gamete • Law of Independent Assortment: genes for different traits are inherited independently from each other

3. Review of Simple Mendelian Genetics • Dominant vs. Recessive alleles for a gene • Dominant allele is represented as a capital letter (R) • Recessive allele is represented as a lowercase letter (r) • The dominant allele masks the recessive one, so you see the dominant trait (for RR or Rr) • The only way to see a recessive trait is to have two recessive alleles (rr)

4. Punnett Square: Monohybrid cross • Remember this?? • Mono=1 (we’re looking at just 1 trait here)

5. Unfortunately, it’s not all that easy…

6. Incomplete Dominance • Sometimes neither allele is fully dominant over the other • Incomplete Dominance: neither allele is dominant but combine and display a new trait that is a mixing of the two alleles • Looks like the intermediate between the two colors (Red ; White = Pink)

7. Incomplete Dominance RR R’R’ RR’ RR’ RR RR’ R’R’

8. Thinking Cap • What do you notice looks the same with regard to the “simple” genetics of last week? • What do you notice looks different? Why might that be the case?

9. Incomplete Dominance • In incomplete dominance, the two alleles are represented as • Two capital letters, one with an apostrophe to indicate the different allele that is involved • Ex. R (for the red allele) and R’ (for the white allele) • When these two alleles come together, they portray a blending of the two phenotypes!

10. Copy on 5L:INCOMPLETE DOMINANCE R R R’ R’ All offspring have this genotype: _____ All offspring have this phenotype: ____________

11. Sum it up (5L): • 3 word summary • 2 descriptive words • 1 “hashtag”

12. Codominance • Other times both alleles are fully dominant • Codominance: both alleles of a gene are dominant and the heterozygous phenotype has both traits equally expressed • Looks spotted / speckled

13. Codominance x BB WW BW

14. Thinking Cap • What do you notice looks the same with regard to the “simple” genetics of last week? • What do you notice looks different? Why might that be the case?

15. Codominance • In codominance the two alleles are represented as • Two different capital letters: Use the first letter of one trait (ex: B for Brown) and the first letter of the other trait (ex: W for White) • When they come together as a heterozygote, both traits show (as speckles / spots / ombre / etc.) in the phenotype

16. Copy on 5L:CODOMINANCE B B W W All offspring have this genotype: _____ All offspring have this phenotype: ____________

17. Sum it up (5L): • 3 word summary • 2 descriptive words • 1 “hashtag”

18. Quick Quizzy time! • Let’s say there are two alleles for the hair color trait- red and blue • What would be the resulting phenotype of a heterozygous pair if the alleles showed incompletedominance? • A. Red • B. Blue • C. Purple • D. Red and Blue patches

19. Quick Quizzy time! • Let’s say there are two alleles for the hair color trait- red and blue • What would be the resulting phenotype of a heterozygous pair if the alleles showed codominance? • A. Red • B. Blue • C. Purple • D. Red and Blue patches

20. Quick Quizzy time!