1. Mendel and Meiosis Chp 10 Pp. 252-279

2. Contents 10-2 Meiosis 10-1 Mendel

3. Chromosome Rod shaped structures made of DNA and proteins Carrier of genetic material Located in the nucleus Copied and passed from generation to generation

5. Chromosomes Sex chromosomes: chromosomes that determine the sex of an organism Humans X and Y Females: X X Males: X Y Autosomes: all other types of chromosomes

6. Chromosomes

7. Homologous Chromosomes 2 copies of each autosome Same size and shape Carry genes for the same trait Ex. If 1 homologous chromosome contains gene for eye color the other homologous chromosome will too.

8. Homologous Chromosomes

9. Diploid Cell Cell with 2 sets of chromosomes Contains chromosomes for each homologous pair Somatic Cells= Body Cells: Diploid All human cells except sex cells are diploid. One from each parent 2n Humans 2n = 46

10. Haploid Cell containing one of each kind of chromosome Sperm and egg cells = Gametes 1 set of chromosomes Half the number of chromosomes of diploid n Sperm + Egg = Zygote n + n = 2n

11. Mitosis vs. Meiosis Mitosis: t = two: Diploid 2n=46 Meiosis: o = one: Haploid » n = 23

12. Meiosis Gametes are produced in specialized body cells Produces Sperm and Egg Cells 2 divisions: Meiosis I and Meiosis II Meiosis occurs in sex cells, not body cells Results in 4 daughter cells Each cell has half the chromosomes of the parent

13. Meiosis I Interphase occurs: the cell grows and DNA replicates Meiosis I begins Original cell produces two new cells

14. Prophase I DNA Coils tightly into chromosomes spindle fibers appear Each chromosome lines up next to the homologue Synapis occurs: pairing of homologous chromosomes Tetrad: Each pair of homologous chromosomes

15. Crossing Over Crossing Over: why we do not look exactly like our parents.Crossing Over: why we do not look exactly like our parents. Portions of the chromatid breaks off and attaches to adjacent chromatids on the homologous chromosome Permits the exchange of genetic material between maternal and paternal chromosomes Occurs during Prophase

17. Genetic Recombination Crossing over produces a new mixture of genetic material Occurs during Prophase

18. Causes of Variation Chromosomes are assorted randomly Crossing over may occur Cells do not have identical genetic info as each other or the parent Good: more chance of survival and evolution Bad: mistakes more likely

19. Metaphase I Tetrads line up randomly along the mid-line Spindle fibers attach to centromeres

20. Anaphase I Homologous chromosomes move to the opposite poles Random separation or Independent Assortment results in separation of maternal and paternal chromosomes.

21. Telophase I Chromosomes reach opposite ends of cell Cytokinesis begins cell is haploid

22. Meiosis II Occurs in each cell formed in Meiosis I Interphase does not occur again

23. Prophase II Spindle fibers form and move the chromosomes to the mid-line of the dividing cell

24. Metaphase II Chromosomes move to the mid- line of the dividing cell facing opposite poles of the dividing cell

25. Anaphase II Chromatids separate and move to opposite poles of the cell

26. Telophase II Nuclear membrane forms around the chromosomes in each of 4 new cells

27. Cytokinesis II Cytoplasm divides Cell Membrane closes off

28. End Result: Four new cells that contain half of the original cells number of chromosomes 4 sex cells are created

29. Meiosis Animation

31. Haploid = one of each kind Diploid = two of each kind 2n = diploidn = haploid

32. WHY DO WE NEED HAPLOID? EGG 23 SPERM Female gamete Male gamete 23

33. Fertilization restores the diploid number 2n 1n 1n 2n fertilization meiosis Mitosis and cell growth

34. Gametes formed by meiosis haploid reproductive cells humans: meiosis occurs in the testes and ovaries

35. Spermatogenesis: Male

36. Oogenesis: Female One Mature Egg Cell

37. Human Karotype

38. Asexual Reproduction Production of offspring from one parent Does not involve meiosis Offspring are genetically identical to parent

39. Sexual Reproduction Production of offspring through meiosis and the union of sperm and egg Offspring are genetically different form parents Genes are combined in new ways in meiosis Evolutionary advantage is that it enables species to rapidly adapt to new conditions

41. Mitosis vs. Meiosis Mitosis vs. Meiosis Animation

42. Nondisjunction Failure of homologous chromosomes to separate properly during meiosis. Both chromosomes of a homologous pair move to the same pole of the cell. 1 gamete has an extra chromosome Or 1 gamete is missing a chromosome

43. Nondisjunction Animation

44. 10-1 Mendel Gregor Mendel Austrian monk Studied how traits are inherited from parents to offspring Father of heredity Chose garden peas for his meticulous experiments

45. Garden Peas Reproduce sexually W/ male & female gametes (sex cells) Fertilization results in zygote Becomes seed Pollination male pollen transferred to female pistil

46. Monohybrid Cross Hybrid- offspring of parents with different forms of a trait Tall or short crossed true-bred tall plants w/ true- bred short plants to get heterozygous offspring which then self-pollinated

47. Some Genes are Dominant Some Genes Are Dominant click to playSome Genes Are Dominant

48. Seven Traits of Peas

49. Mendel’s Rules Alleles- different gene forms Rule of Dominance –Dominant –observed trait –Recessive- disappearing or hidden trait

50. Mendel’s Rules Law of Segregation Every individual has 2 alleles of each gene w/ each gamete receiving 1. During fertilization, gametes randomly pair to produce four combinations

51. Phenotypes & Genotypes Appearance= Phenotype Allele combination= Genotype Homozygous-Both alleles alike Heterozygous- different alleles, one dominant & one recessive

52. Mendel’s Dihybrid Cross

53. Law of Independent Assortment Says that genes for different traits are inherited independently from each other. The alleles can recombine in four different ways.

54. Punnett Squares Shorthand way to find possible genotypes from crossing two known parents. Two heterozygous parents produce 1 homozygous dominant: 2 heterozygous:1 homozygous recessive 1BB: 2Bb:1bb