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Mendel observed traits that: A. inherited B. are determined by one gene

Mendel observed traits that: A. inherited B. are determined by one gene C. have two phenotypes only D. one phenotype dominant, one recessive. Can you think of traits that do NOT behave this way? Explain your choice. Cases when Mendel’s Law of dominance does not apply:

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Mendel observed traits that: A. inherited B. are determined by one gene

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  1. Mendel observed traits that: A. inherited B. are determined by one gene C. have two phenotypes only D. one phenotype dominant, one recessive. Can you think of traits that do NOT behave this way? Explain your choice.

  2. Cases when Mendel’s Law of dominance does not apply: 1) IncompleteDominance One allele is partially dominant over the other. 2)Co-Dominance Both alleles contribute to the phenotype.

  3. INCOMPLETEDOMINANCE Case of the Snapdragons

  4. How to make a pink flower?

  5. R1R1 R2R2 Generation: P Incomplete dominance: R1R2 F1

  6. R1R2 R1R2 ? R1R1 R1R2 R1R2 R2R2

  7. Comparing punnet squares: • one of Mendel’s peas • (complete dominance) • one of Snapdragon Flowers • (incomplete dominance) • (R1=Red, R2=White, R1R2=pink).

  8. Incomplete Dominance Dominance ≠ R1R2 x R1R2 Pp x Pp P p R1 R2 P R1 p R2

  9. Complete dominance: Phenotypic ratio would be 3:1(Purple:White) Incomplete dominance: Phenotypic ratio would be 1:2:1 (Red:Pink:White flowers), just like the genotypic ratio.

  10. CO-DOMINANCE Case of the Roan horses And ABO blood groups

  11. Roan Horses

  12. Roan fur: An example of co-dominance Both (brown and white) alleles show up

  13. Chromosome 9 3 Alleles: IA IB i Antigen A Antigen B none

  14. Human ABO Blood Groups: - Three possible alleles: IA IB i Genotype: Phenotype: A IA IA B IB IB O i i A IA i B IB i IA IB AB

  15. ABO Punnet Square exercise, handout

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