Gregor Mendel studied inheritance through pea plant experiments in the 1800s. He found that traits are determined by discrete factors, now called genes, which are passed from parents to offspring. Traits are dominant or recessive, with dominant traits expressed when either one or two copies are present and recessive traits only expressed with two recessive copies. During meiosis, alleles segregate so offspring receive one of each from parents randomly. Punnett squares can predict genotypic and phenotypic ratios by combining possible gametes.

1. 11.1-11.2 Gregor Mendel &Punnett Squares Pages 262 - 266 PD -old

2. Goal 1 Describe how Mendel Studied inheritance in peas

3. Austrian Monk 1800’s Taught High School Managed monastery gardens

4. Pea plant observations True-breeding plants Self pollination = offspring identical to parents

5. Cross pollination used to study inheritance Tall plant x short plant Green seeds x yellow seeds

6. Goal 2 Summarize Mendel’s conclusions about inheritance

7. Results of Mendel’s experiment Cross pollination of true breeding parents (P) Offspring (F1) only show one trait No “blending” of traits Tall plant x short plant = all tall plants P P F1

8. Mendel’s 1 st conclusions about inheritance Inheritance determined by factors passed from one generation to the next Each trait determined by one gene that occurs in two different forms ( alleles ) Trait of height located on one gene as either short or tall alleles

9. Goal 3 Explain the principle of dominance

10. He tried again with F1 generation Cross pollination of F1 offspring ¾ F2 offspring show one trait ¼ F2 show “hidden” trait F1 x F1 = F2 Tall plant x Tall plant = 3/4 tall plants ¼ short plants

11. Creative commons Image credit: Madprime

12. Principle of dominance states: some alleles are dominant and others are recessive If dominant allele present, it will be expressed Recessive alleles only expressed if NO dominant allele present

13. Goal 4 Describe what happens to alleles during segregation in meiosis

14. Alleles separate during meiosis Alleles segregate into one allele per gamete Two types of gametes can be produced Alleles pair up randomly when gametes unite during fertilization

15. Example on the board…

16. Goal 5 Use Punnett Squares to: determine genotypic and phenotypic ratios of a cross to Predict outcomes

17. Phenotype = the expressed physical trait What can be seen (brown hair) Dependent on genotype Genotype = the alleles of a genetic code Genetic code (one maternal, one paternal) Homozygous = alleles are the same (BB or bb) Heterozygous = alleles are different (Bb)

18. Recessive phenotype Genotype MUST be homozygous recessive Genotype bb expresses phenotype blond hair Dominant phenotype Genotype may be homozygous dominant BB expresses brown hair Genotype may be heterozygous Bb also expresses brown hair

19. Genotypes are used to create Punnett Squares and compare possible combinations of gametes Parent 1 gamete possibilities Parent 2 gamete possibilities Possible Combination Possible Combination Possible Combination Possible Combination

20. B b b B Parent 1 : homozygous dominant Parent 2 : homozygous recessive Bb Bb Bb Bb

21. B b B b Parent 1 : heterozygous Parent 2 : heterozygous bb Bb BB Bb

22. B b B b Genotypic ratio of offspring 1BB : 2Bb : 1bb Phenotypic ratio of offspring 3 brown hair : 1 blond hair (75% chance) (25% chance) bb Blond hair Bb Brown hair BB Brown hair Bb Brown hair

23. ? ? ? ? Parent 1 : heterozygous (Bb) Parent 2 : homozygous recessive (??) ?? ?? ?? ??

24. B b b b Parent 1 : heterozygous (Bb) Parent 2 : homozygous recessive ( bb ) bb Bb Bb bb

25. B b b b bb Bb Bb bb Genotypic ratio of offspring ?? : ?? Phenotypic ratio of offspring ?? : ??

26. B b b b bb Bb Bb bb Genotypic ratio of offspring 2Bb : 2bb Phenotypic ratio of offspring 2 brown hair : 2 blond hair (50% chance) (50% chance)

27. Thanks to the following people who have generously shared images on Flickr creative commons: Unertlkm… pea plant Z e n… butterfly and pea bloom