CHAPTER 11 Introduction to Genetics

1. CHAPTER 11Introduction to Genetics

2. Genetics- the scientific study of heredity Gregor Mendel

3. Gregor Mendel’s work Fertilization- sexual reproduction, union of male and female reproductive cells True-breeding- to produce offspring that are identical to the parents in characteristics

4. Gregor Mendel’s work Cross-pollination- taking the sperm cells from one plant and joining them with the egg cells of another plant

5. Gregor Mendel’s work Trait- specific characteristic P generation- Parental generation F1 generation- offspring of first generation F1 “first filial” Hybrids- offspring of parents with different traits

6. Conclusions 1. Biological inheritance is determined by factors that are passed from one generation to the next Genes- chemical factors that determine traits ex: the gene for plant height Alleles- different forms of a gene ex: the short allele and the tall allele

7. Conclusions 2. Principle of dominance some alleles are dominant and some are recessive

8. Segregation What happened to the traits of the P generation that disappeared in the F1 generation?

9. Segregation F2 generation- the F1 generation self-pollinated

10. Segregation The gametes (sex cells) contain only one of the traits. The gametes separate the traits and recombine them in the offspring

11. 11-2 Probability and Punnett Squares • Probability- the likelihood that a particular event will occur

12. Punnett Squares • Can be used to predict and compare the genetic variations that will result from a cross

13. Homozygous- two identical alleles for a particular trait. Ex: TT or tt • Heterozygous- two different alleles for a particular trait. Ex: Tt • Phenotype- physical characteristics • Tall plants or short plants • Genotype- genetic makeup • TT, tt, or Tt

14. Can two organisms have the same phenotype but a different genotype?

15. Probabilities predict averages • Increasing the number of offspring yields results closer to the predicted averages

16. 11-3 Exploring Mendelian Genetics • Independent Assortment • Does the segregation of one pair of alleles affect the segregation of another pair of alleles? • Round Yellow X Wrinkled Green

17. Round Yellow X Wrinkled Green • All the F1 generation were round yellow • Which traits are dominant?

18. F2 generation, RrYy X RrYy

19. F2 generation, RrYy X RrYy

20. F2 generation, RrYy X RrYy • Round Yellow

21. F2 generation, RrYy X RrYy • Round Yellow • Round Green

22. F2 generation, RrYy X RrYy • Round Yellow Wrinkled Yellow • Round Green

23. F2 generation, RrYy X RrYy • Round Yellow Wrinkled Yellow • Round Green Wrinkled Green

24. 9: 3: 3: 1 Ratio • Round Yellow Wrinkled Yellow • Round Green Wrinkled Green

25. Independent Assortment • Genes for different traits can segregate independently during the formation of gametes.

26. Beyond Dominant and Recessive Alleles • Incomplete Dominance

27. Beyond Dominant and Recessive Alleles • Incomplete Dominance – neither allele is dominant

28. Beyond Dominant and Recessive Alleles • Incomplete Dominance – neither allele is dominant

29. Beyond Dominant and Recessive Alleles • Incomplete Dominance – neither allele is dominant

30. Beyond Dominant and Recessive Alleles • Codominance- both alleles contribute to the phenotype • Ex: Brown mated with white creates a mixture of brown and white (roan)

31. Beyond Dominant and Recessive Alleles • Multiple Alleles- genes that have more than two alleles • Ex: Human blood types • Blood phenotypes: A, B, AB, O

33. Polygenic Traits- Phenotype is controlled by many different genes • Ex: Skin color is controlled by at least three different genes

34. Thomas Hunt Morgan • Fruit Flies (Drosophila melanogaster) • Ideal for genetics experiments: • Reproduce quickly • Large # of offspring • Small in size

35. Nature vs. Nurture • Which has a greater influence on an organism, the DNA or the environment?

36. Nature vs. Nurture Phenotype often depends on genes and the environment. • Humans: • Height- nutrition • Strength- exercise • Skin color- exposure to sunlight • Intelligence- experience

37. 11-4 Meiosis Chromosome Number Fruit Fly has 8 chromosomes 4 from father 4 from mother Homologous chromosomes- same type of chromosome The 4 chromosomes from the male parent are homologous to the 4 chromosomes from the female parent.

38. Diploid vs. Haploid • Diploid- a cell that contains two sets of homologous chromosomes. 2N • Fruit flies: 2N= 8 Humans: 2N=46 Most adult cells are diploid. Haploid- a cell that contains one set of chromosomes. N Fruit flies: N= 4 Humans: N=23 Gametes (sex cell: sperm, egg) are haploid.

39. Phases of Meiosis • Meiosis- the process of the number of chromosomes per cell is cut in half in the production of daughter cells by the separation of homologous chromosomes

40. Phases of Meiosis

41. Phases of Meiosis 2N 2N 4N 2N N 2N N N 2N N

42. Phases of Meiosis 2N 2N 4N 2N N 2N N N 2N N

44. Phases of Meiosis 2N 2N 4N 2N

45. Tetrad- a structure of two homologous chromosomes, 4 sister chromatids • Occurs during Prophase I • Crossing over- process of exchanging portions of sister chromatids

47. Crossing over creates many unique combinations of gamete cells.

48. Sperm production N 2N N 2N 4N N 2N N Egg production N 2N N Polar Body 2N 4N N Polar Body 2N N Polar Body

49. Zygote Formation • Egg and Sperm join together to form a zygote • Egg= N • Sperm= N • Zygote = 2N

50. 11-5 Linkage and Gene Maps T T T TT TT T T T T T T T T T t TT t t t T t T T t t