1. Mendelian Genetics

2. What Came Before? Blending Inheritance Inheritance of Acquired Characteristics

3. Mendel’s Model Organism Advantages of pea plants for genetic study: o There are many varieties with distinct heritable features, or traits (such as peacolor) o Mating of plants can be controlled o Quick generation time; lots of offspring o Can isolate true-breeding lines for particular traits

4. Fig. 14-2a Stamens Carpel Parental generation (P) TECHNIQUE 1 2 3 4

5. Fig. 14-3-3 EXPERIMENT P Generation (true-breeding parents) Purple flowers White flowers  F 1 Generation (hybrids) All plants had purple flowers F 2 Generation 705 purple-flowered plants 224 white-flowered plants

6. Table 14-1

7. CONCEPT 1: There are alternative versions of “heritable factors”

8. Fig. 14-4 Allele for purple flowers Homologous pair of chromosomes Locus for flower-color gene Allele for white flowers

9. CONCEPT 2: For each trait, an organism inherits two alleles, one from each parent

10. Fig. 14-4

11. CONCEPT 3: If the two alleles at a locus differ, then one (the dominant allele) determines the organism’s appearance, and the other (the recessive allele) has no noticeable effect on appearance

12. Fig. 14-3-3 EXPERIMENT P Generation (true-breeding parents) Purple flowers White flowers  F 1 Generation (hybrids) All plants had purple flowers F 2 Generation 705 purple-flowered plants 224 white-flowered plants

13. Misconceptions About Dominant vs. Recessive Dominant alleles are not necessarily more common in populations than recessive alleles Dominant alleles are not necessarily “better” / adaptive Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

14. CONCEPT 4: Law of Segregation

15. Fig. 14-5-3 P Generation Appearance: Genetic makeup: Gametes: Purple flowers White flowers PP P pp p F 1 Generation Gametes: Genetic makeup: Appearance: Purple flowers Pp P p 1/21/2 1/21/2 F 2 Generation Sperm Eggs P P PPPp p p pp 31

17. How can you tell the genotype of an individual with the dominant phenotype?

18. CONCEPT 5: Law of Independent Assortment

19. Fig. 14-8 EXPERIMENT RESULTS P Generation F 1 Generation Predictions Gametes Hypothesis of dependent assortment YYRRyyrr YR yr YyRr  Hypothesis of independent assortment or Predicted offspring of F 2 generation Sperm YR yr Yr YR yR Yr yR yr YR YYRR YyRr YYRr YyRR YYrr Yyrr yyRR yyRr yyrr Phenotypic ratio 3:1 Eggs Phenotypic ratio 9:3:3:1 1/21/2 1/21/2 1/21/2 1/21/2 1/41/4 yr 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 3/43/4 9 / 16 3 / 16 1 / 16 Phenotypic ratio approximately 9:3:3:1 31510810132

20. Fig. 14-3-3 EXPERIMENT P Generation (true-breeding parents) Purple flowers White flowers  F 1 Generation (hybrids) All plants had purple flowers F 2 Generation 705 purple-flowered plants 224 white-flowered plants

21. Mendel’s Laws Translated Into Math Multiplication rule = the probability that two or more independent events will occur together is the product of their individual probabilities (AND) Addition rule = the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities (OR)

22. Fig. 14-9 Rr  Segregation of alleles into eggs Sperm R R R R R R r r r r r r 1/21/2 1/21/2 1/21/2 1/21/2 Segregation of alleles into sperm Eggs 1/41/4 1/41/4 1/41/4 1/41/4

23. Example: BbEe x BbEe What is the probability the offspring will be homozygous recessive for both traits? What is the probability the offspring will be homozygous recessive for at least one trait?

24. Example: BbEe x BbEe

25. PRACTICE PROBLEMS!