11-3 Exploring Mendelian Genetics

1. 11-3 Exploring Mendelian Genetics Page 270

2. Think about it…. • Mendel wondered if alleles sorted independently… • ….for example… • “…is the gene for green/yellow peas linked to the gene for round/wrinkled peas….. • …..like….are green peas always round….or….. • …hmmmm…”

3. A. Independent Assortment • 1. Mendel performed an experiment, to follow two genes going from one generation to the next, called a two-factor (dihybrid) cross.

4. A. Independent Assortment • 2. First, Mendel crossed true-breeding (Homozygous) plants. Two-Factor Cross: F1 • 3. Genotypes: RRYY and rryy • Phenotypes: Round/Yellow & Wrinkled/Green.

5. A. Independent Assortment • 4. All the F1 offspring had the genotypeRrYy (heterozygous) and phenotype round/yellow.

6. A. Independent Assortment • 5. Two-Factor Cross: F2 Mendel found that some of the offspring looked NOTHING like the parents!!

7. A. Independent Assortment • 6. In conclusion ALL of a gamete’s alleles segregate independently; known as independent assortment.

8. A. Independent Assortment • 7. Mendel’s results closely matched the expected ratio of 9:3:3:1. 9: Round and Yellow 3: Round and Green 3: Wrinkled and Yellow 1: Wrinkled and Green

9. In mice the ability to run normally is a dominant trait. Mice with this trait are called running mice ( R ). The recessive trait causes mice to run in circles. Mice with this trait are called waltzing mice ( r ). Hair color is also an inherited trait in mice. Black hair ( B ) is dominant over brownhair ( b ).

10. running mice (R), waltzing mice (r), Black hair (B), brownhair (b). • 1. Cross a heterozygous running heterozygous black mouse with a homozygous running, homozygous black mouse.

11. running mice (R), waltzing mice (r), Black hair (B), brownhair (b). • 2. Cross a homozygous running, homozygous black mouse with a heterozygous running, brown mouse.

12. running mice (R), waltzing mice (r), Black hair (B), brownhair (b). • 3. Cross a homozygous waltzing brown mouse with a homozygous waltzing brown mouse.

13. running mice (R), waltzing mice (r), Black hair (B), brownhair (b). • 4. Cross a homozygous running, heterozygous black mouse with a homozygous waltzing brown mouse.

14. running mice (R), waltzing mice (r), Black hair (B), brownhair (b). • 5. Cross a homozygous running, brown mouse with a heterozygous running, homozygous black mouse.

15. running mice (R), waltzing mice (r), Black hair (B), brownhair (b). • 6. Cross a heterozygous running, heterozygous black mouse with a heterozygous running, heterozygous black mouse.

16. B. A Summary of Mendel’s Principles • 1. Genes are passed from parents to offspring. • 2. When there are 2 alleles (form of a gene), 1 is dominant and 1 is recessive.

17. B. A Summary of Mendel’s Principles • 3. Most organisms have two copies of a gene, one from each parent, that are segregated when gametes are formed (meiosis).

18. B. A Summary of Mendel’s Principles • 4. Alleles segregate independently from each other (independent assortment).

19. How do you think this happens??

20. C. Beyond Dominant and Recessive Alleles • 1. Some alleles are neither dominant or recessive, many traits are controlled by multiple genes or alleles.

21. C. Beyond Dominant and Recessive Alleles Ex: Flower color. Red=AA, White= aa, Pink= Aa • 2. Incomplete dominance occurs when one allele is not completely dominant over another. (The heterozygous phenotype is between the homozygous dominant and homozygous recessive phenotypes.)

22. C. Beyond Dominant and Recessive Alleles • 3. Codominance occurs when both alleles contribute to the phenotype. • Ex: Blood Types

23. C. Beyond Dominant and Recessive Alleles • 4. Some genes have multiple alleles to create a phenotype. • Ex: Fur Color in Rabbits

24. C. Beyond Dominant and Recessive Alleles • 5. Polygenic Traits are traits controlled by 2 or more genes. • Ex: Skin tone is controlled by 4 genes.

25. C. Beyond Dominant and Recessive Alleles • 6. Sex-Linked Traits express their phenotype based on the sex chromosomes. • EX: Colorblindness

26. Matching • 1. Incomplete Dominance • 2. Codominance • 3. Multiple Alleles • 4. Polygenic Traits • 5. Sex-Linked Traits • A. Colorblindness • B. Skin Tone • C. Blood Type • D. Rabbits Fur • E. Flower color

27. D. Applying Mendel’s Principles

28. E. Genetics and the Environment