Heredity – or What did Mendel do?

1. Heredity – or What did Mendel do? Honors biology

2. Gregor Mendel • Discuss, then share with the class what you CURRENTLY know about Mendel. • 5 minutes

3. Mendel’s main points: • Physical traits are determined by “factors” (genes) that are passed down by both parents. • These “factors” are passed down in predictable patterns from one generation to the next.

4. Other points • Mendel grew pea plants to determine what “traits” were passed on to offspring. (chose 7 traits to study) • He did not know about genes.

5. Mendel’s Generations • Parent Generation – the original breeding plants (parents) • F1 Generation – the first “offspring” that resulted. • F2 Generation – the “offspring” that result from mating 2 of the F1 Generation plants

6. Mendel’s peas – flower color only

7. Vocabulary • Traits – features that make up who you are (determined by your genes) • Phenotype – physical makeup (example – brown hair, pointy ears) • Genotype – genetic makeup (example – genes on chromosomes)

8. Alleles • An alternative form of a gene (one member of a pair of chromosomes) that is located at a specific position on a specific chromosome. • Organisms have 2 alleles for each trait: HH, Hh, or hh (each letter is an allele)

9. Alleles

10. Genotypes • Dominant versus Recessive alleles • Homozygous dominant, Heterozygous, Homozygous recessive • What are these?? Hh, hh, HH

11. The Law of Segregation • Alleles for a trait separate when gametes form during meiosis. • Gametes have only one allele for each trait.

12. Law of Independent Assortment • Allele pairs separate independently during the formation of gametes. • Example – the gene for hair color is passed on to offspring independently from eye color.

13. Inheritance • You inherited genes from both your father and your mother. • Meiosis – because of “crossing over”, each time your parents had a child, different traits were passed on.

14. Crossing over

15. Monohybrid Cross – Parents

16. Monohybrid Cross – F1

17. Mendel’s peas (flower color) (PP) (pp) (All Pp) Phenotype: 3 purple, 1 white Genotype: 1 PP, 2 Pp, 1 pp

18. Monohybrid crosses – Punnett squares * * *(Possible alleles to pass down)

19. Practice Cross a homozygous male for pointy ears with a heterozygous female for pointy ears. (use letter “e”) Pointy ears are dominant over non-pointy ears. Phenotype ratio: Genotype ratio:

20. Answer E E Genotype ratio: 2:2 or 50% EE, 50% Ee (2 = EE, 2 = Ee) But…reduce ratio to 1:1 EE EE E e Ee Ee Phenotype ratio: 4:0 pointy ears or 100%

21. Practice • Work on practice sheet together. Tomorrow we will learn how to do dihybrid crosses and also practice.

22. Dihybrid Crosses

23. How to set it up and read it… (GgBb) (GgBb)

24. Answer - volunteer Genotypic ratio: Phenotypic ratio: