1. 11-1 The Work of Mendel What does every living thing inherit from their parents? Genetics – the study of heredity Look around at your classmates and make a list of some of the traits that are inherited.

2. What did Mendel already know… Each flower produces pollen (sperm) and egg cells Cross fertilization (sexual) – male and female cells join Self-pollination (asexual) – pollen fertilizes eggs from same plant Mendel’s pea plants were true-breeding –A tall plant with green seeds would produce a tall plant with green seeds

3. Genes, Alleles and Dominance Trait – specific characteristic –Mendel studied 7 different pea plant traits What are some examples? Plant Height, Seed Shape, Pod Color

4. Genes, Alleles and Dominance Genes – the chemical factors that determine traits (the segment of DNA) ex. pea plant: height Alleles – different forms of a gene from each parent ex. pea plants: tall and short (T or t)

5. Principle of Dominance Principle of dominance: some alleles are dominant and others are recessive Dominant allele – the trait is always shown –Capital letter (T = tall) Recessive allele – the trait that will only show if there is no dominant allele –Lower case letter (t = short)

6. Heterozygous – organisms that have 2 different alleles for the same trait –Hybrid for that trait –Ex: Tt Homozygous – organisms that have 2 identical alleles for a particular trait True-breeding for a particular trait –Ex: TT or tt

7. Genes, Alleles and Dominance Phenotype – physical characteristics –Ex: tall, short, yellow, green Genotype – genetic make-up –Ex: TT, Tt, tt Tall plants have the same phenotype (tall), but not the same genotype (TT or Tt) Why are TT and Tt genotypes for tallness, but tt is not???

8. Mendel crossed plants to study offspring P generation – (parents, originals) – Tall x short F1 generation – (offspring of P) tall x tall F2 generation – (offspring of F1) 3 tall, 1 short

9. 11-2 Probability and Punnett Squares Mendel realized…the principles of probability could be used to explain the results of genetic crosses.

10. Genetics and Probability Probability – the likelihood a particular event will occur. –Ex: probability of flipping a coin to heads = ½ or 50% –Probability of head 3 times in a row = ½ x ½ x ½ = 1/8 –The greater the number or trials, the closer to the expected ratio –Past outcomes do not affect future outcomes Alleles segregate randomly (like a coin)

11. Probabilities Predict Averages To get an accurate prediction of flipping a coin – the coin should be flipped many times and an average taken. In genetics …the more offspring you get, the closer to the predicted ratio.

12. Principle of Segregation Segregation = separation The alleles for tall vs. short separate during the formation of gametes – sex cells Each gamete carries one allele for each gene

13. Principle of Independent Assortment Mendel questioned how alleles segregate Does it happen independently? Ex: Does the seed shape gene influence the seed color gene???? INDEPENDENT ASSORTMENT Need to follow 2 diff. alleles from one generation to the next.

14. The Two-factor Cross: F1 4 alleles (2 genes) at the same time Provides the hybrid plants (F2 generation) Crossed a homozygous RRYY (round yellow peas) with a homozygous rryy (wrinkled, green peas)

15. The two factor cross: F2 F1 – yields all offspring heterozygous for both traits F2 – heterozygous parents crossed F2 – yields 9:3:3:1 ratio

16. Mendel discovered the principle of Independent assortment – genes segregate independently during the formation of the gametes –Helps account for many genetic variations in organisms –Seed shape & color gene do not influence each other

17. Meiosis

18. Ttrr x ttRr

19. ttRr x TtRr