1. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 8 The Cellular Basis of Reproduction and Inheritance

2. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings a)State the names of the parts of the chromosome labelled (i) and (ii) on the diagram below (2) (b)Explain how the inheritance of chromosome 21 can lead to Down’s syndrome. (3) (c)Explain how meiosis promotes variation in a species. (2) (Total 7 marks)

3. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings (a)(i)centromere; (ii)sister chromatids / chromatids;2 Do not accept chromosome(s). (b)non-disjunction; the failure of homologues / sister chromatids to separate during meiosis; anaphase I / anaphase II; two copies of chromosome 21 in gamete; fertilization leads to trisomy / trisomy 21;3 max (c)crossing over (in prophase I) leads to new combinations of alleles; random alignment of homologues (at metaphase I) produces new chromosome combinations / independent assortment;2 max

4. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Online Video: MEIOSIS Online Video: MEIOSIS

5. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings MEIOSIS AND CROSSING OVER 8.12 Chromosomes are matched in homologous pairs somatic (body) cells of each species –specific # of chromosomes human cells have … –46 –23 pairs of homologous chromosomes

6. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings chromosomes of a homologous pair –Carry genes for same characteristics at same place, or locus Chromosomes Centromere Sister chromatids Figure 8.12

7. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.13 8.13 Gametes have a single set of chromosomes Cells with 2 sets of chromosomes –Are said to be diploid Gametes, eggs and sperm, are haploid –single set of chromosomes

8. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Sexual life cycles –alternation of haploid and diploid stages Mitosis and development Multicellular diploid adults (2n = 46) Diploid zygote (2n = 46) 2n2n Meiosis Fertilization Egg cell Sperm cell n Haploid gametes (n = 23) n Figure 8.13

9. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.14 Meiosis 8.14 Meiosis reduces chromosome # from diploid to haploid Meiosis, similar to mitosis b/c –preceded by chromosome duplication BUT in meiosis –cell divides twice to form 4 daughter cells CD Animation: MEIOSIS CD Animation: MEIOSIS

10. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1 st division, meiosis I –Starts with synapsis, the pairing of homologous chromosomes In crossing over –Homologous chromosomes exchange corresponding segments End of Meiosis I –each homologous pair separates –2 daughter cells, each with 1 set of chromosomes

11. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Meiosis IIMeiosis II is ~~same as mitosis –sister chromatids of each chromosome separate –result = 4 haploid cells

12. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings MEIOSIS I: Homologous chromosomes separate INTERPHASE PROPHASE I METAPHASE I ANAPHASE I Centrosomes (with centriole pairs) Sites of crossing over Spindle Microtubules attached to kinetochore Metaphase plate Sister chromatids remain attached Nuclear envelope Chromatin Sister chromatids Tetrad Centromere (with kinetochore) Homologous chromosomes separate Figure 8.14 (Part 1)

13. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PROPHASE II METAPHASE II ANAPHASE II TELOPHASE I AND CYTOKINESIS TELOPHASE II AND CYTOKINESIS Cleavage furrow Haploid daughter cells forming Sister chromatids separate MEIOSIS II: Sister chromatids separate Figure 8.14 (Part 2)

14. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings MitosisMeiosis Parent cell (before chromosome replication) Chromosome replication Chromosomes align at the metaphase plate Tetrads align at the metaphase plate Sister chromatids separate during anaphase Homologous chromosomes separate during anaphase I; sister chromatids remain together No further chromosomal replication; sister chromatids separate during anaphase II Prophase Metaphase Anaphase Telophase Duplicated chromosome (two sister chromatids) Daughter cells of mitosis 2n2n 2n2n Daughter cells of meiosis I n n n n 2n = 4 Tetrad formed by synapsis of homologous chromosomes Meiosis i Meiosis ii Prophase I Metaphase I Anaphase I Telophase I Haploid n = 2 Daughter cells of meiosis II 8.15 Review: comparison of mitosis & meiosis Figure 8.15

15. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings THURSDAY, 3/11/10 Outline the differences between the behaviour of the chromosomes in mitosis and meiosis. (Total 5 marks)

16. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5 marks from your SENTENCES two divisions in meiosis, only one in mitosis; meiosis results in haploid cells, mitosis in diploid cells; crossing over only occurs in meiosis; no S phase precedes meiosis II; chromosome behaviour in meiosis II and mitosis is similar / chromosome behaviour in meiosis I and mitosis is different; chiasmata only form during meiosis; homologous chromosomes move to the equator in pairs only in meiosis; Do not accept number of cells produced - it is a result not a behaviour.

17. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.16 8.16 Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring Each chromosome of a homologous pair –Differs at many points from the other member of the pair CD Animation: Variation in Offspring

18. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Random arrangements metaphase IRandom arrangements of chromosome pairs at metaphase I of meiosis many different combinations of chromosomes in eggs and sperm –  many different combinations of chromosomes in eggs and sperm Combination 1 Combination 2 Combination 3 Combination 4 Gametes Metaphase II Two equally probable arrangements of chromosomes at metaphase I Possibility 1Possibility 2 Figure 8.16

19. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Random fertilizationRandom fertilization of eggs by sperm –Greatly increases this variation

20. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.17 8.17 Homologous chromosomes carry different versions of genes differences between homologous chromosomes –based on: can bear different versions of a gene at corresponding loci…different ALLELES! Tetrad in parent cell (homologous pair of duplicated chromosomes) ec EC White Pink ec ec EC EC Meiosis BlackBrown Chromosomes of the four gametes Eye-color genes Coat-color genes Brown coat (C); black eyes (E) White coat (C); pink eyes (e) Figure 8.17A Figure 8.17B

21. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.18 Crossing over further increases genetic variability Genetic recombination –results from crossing over –during prophase I of meiosis, –increases variation still further Figure 8.18A Chiasma Tetrad Centromere TEM 2,200 

22. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Coat-color genes Eye-color genes Tetrad (homologous pair of chromosomes in synapsis) C E c e C E c e C E c e Chiasma C E C e c E c e C E C e c E c e Parental type of chromosome Recombinant chromosome Parental type of chromosome Gametes of four genetic types How crossing over leads to genetic variation Breakage of homologous chromatids 1 Joining of homologous chromatids 2 3 Separation of homologous chromosomes at anaphase I 4 Separation of chromatids at anaphase II and completion of meiosis Figure 8.18B

23. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE 8.19 photographic inventory of an individual’s chromosomes A karyotypeA karyotype –Is an ordered arrangement of a cell’s chromosomes

24. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Blood culture Fluid Centrifuge Packed red and white blood cells Hypotonic solution Fixative White blood cells Stain Centromere Pair of homologous chromosomes Sister chromosomes 2,600X A blood culture is centrifuged to separate the blood cells from the culture fluid. 1 The fluid is discarded, and a hypotonic solution is mixed with the cells. This makes the red blood cells burst. The white blood cells swell but do not burst, and their chromosomes spread out. 2 Another centrifugation step separates the swollen white blood cells. The fluid containing the remnants of the red blood cells is poured off. A fixative (preservative) is mixed with the white blood cells. A drop of the cell suspension is spread on a microscope slide, dried, and stained. 3 The slide is viewed with a microscope equipped with a digital camera. A photograph of the chromosomes is entered into a computer, which electronically arranges them by size and shape. 4 The resulting display is the karyotype. The 46 chromosomes here include 22 pair of autosomes and 2 sex chromosomes, X and Y. Although difficult to discern in the karyotype, each of the chromosomes consists of two sister chromatids lying very close together (see diagram). 5 Preparation of a karyotype from a blood sample Figure 8.19

25. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 8.20 8.20 An extra copy of chromosome 21 causes Down syndrome A person may have an abnormal # of chromosomes –causes problems

26. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Down syndrome is caused by trisomy 21 –An extra copy of chromosome 21 5,000  Figure 8.20AFigure 8.20B

27. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The chance of having a Down syndrome child –Goes up with maternal age Age of mother 45 5035 3025 40 20 90 0 10 20 30 40 50 60 70 80 Infants with Down syndrome (per 1,000 births) Figure 8.20C

28. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.21 8.21 Accidents during meiosis can alter chromosome number Abnormal chromosome count is a result of nondisjunction –The failure of homologous pairs to separate during meiosis I –The failure of sister chromatids to separate during meiosis II

29. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Nondisjunction in meiosis I Normal meiosis II Gametes n  1 n  1 Number of chromosomes Nondisjunction in meiosis II Normal meiosis I Gametes n  1n  1 n n Number of chromosomes Figure 8.21A Figure 8.21B

30. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Fertilization after nondisjunction in the mother Sperm cell Egg cell n (normal) n + 1 Zygote 2n + 1 Figure 8.21C

31. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 8.22 survival 8.22 Abnormal numbers of sex chromosomes do not usually affect survival Nondisjunction can also produce gametes with extra or missing sex chromosomes –Leading to varying degrees of malfunction in humans but not usually affecting survival Figure 8.22A Poor beard growth Breast Development Under-developed testes Figure 8.22B Characteristic facial features Web of skin Constriction of aorta Poor breast development Under developed ovaries

32. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

33. CONNECTION 8.23 Alterations of chromosome structure can cause birth defects and cancer Chromosome breakage can lead to rearrangementsChromosome breakage can lead to rearrangements –can produce genetic disorders –if the changes occur in somatic cells, cancer

34. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Deletions, duplications, inversions, & translocations Deletion Duplication Inversion Homologous chromosomes Reciprocal translocation Nonhomologous chromosomes “Philadelphia chromosome” Chromosome 9 Chromosome 22 Reciprocal translocation Activated cancer-causing gene Figure 8.23A Figure 8.23C Figure 8.23B

35. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Sordaria Lab Online Sordaria Lab Online Cells Test…Corrections DUE BY 3/24 progress reports…signed, tomorrow MIDTERM EXAM: 3/22, Monday Multiple choice, Cumulative

36. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Rain Forest Rescue Scientists in Hawaii –Have attempted to “rescue” endangered species from extinction

37. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The goals of these scientists were –To promote reproduction to produce more individuals of specific endangered plants Cyanea kuhihewa Kauai, Hawaii

38. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings In sexual reproduction –Fertilization of sperm and egg produces offspring In asexual reproduction –Offspring are produced by a single parent, without the participation of sperm and egg

39. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION 8.1 Like begets like, more or less Some organisms reproduce asexually –And their offspring are genetic copies of the parent and of each other LM 340  Figure 8.1A

40. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Other organisms reproduce sexually –Creating a variety of offspring Figure 8.1B

41. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

42. 8.2 Cells arise only from preexisting cells Cell division is at the heart of the reproduction of cells and organisms –Because cells come only from preexisting cells

43. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.3 Prokaryotes reproduce by binary fission Prokaryotic cells –Reproduce asexually by cell division Colorized TEM 32,500  Prokaryotic chromosomes Figure 8.3B

44. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Prokaryotic chromosome Plasma membrane Cell wall Duplication of chromosome and separation of copies 1 Continued elongation of the cell and movement of copies 2 Division into two daughter cells 3 As the cell replicates its single chromosome, the copies move apart –And the growing membrane then divides the cells Figure 8.3A

45. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings THE EUKARYOTIC CELL CYCLE AND MITOSIS 8.4 The large, complex chromosomes of eukaryotes duplicate with each cell division A eukaryotic cell has many more genes than a prokaryotic cell –And they are grouped into multiple chromosomes in the nucleus

46. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings LM 600  Individual chromosomes contain a very long DNA molecule associated with proteins –And are visible only when the cell is in the process of dividing If a cell is not undergoing division –Chromosomes occur in the form of thin, loosely packed chromatin fibers Figure 8.4A

47. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Before a cell starts dividing, the chromosomes replicate –Producing sister chromatids joined together at the centromere TEM 36,000  Centromere Sister chromatids Figure 8.4B

48. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Cell division involves the separation of sister chromatids –And results in two daughter cells, each containing a complete and identical set of chromosomes Centromere Chromosome duplication Sister chromatids Chromosome distribution to daughter cells Figure 8.4C

49. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.5 The cell cycle multiplies cells The cell cycle consists of two major phases INTERPHASE S (DNA synthesis) G1G1 G2G2 Cytokinesis Mitosis MITOTIC PHASE (M) Figure 8.5

50. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings During interphase –Chromosomes duplicate and cell parts are made During the mitotic phase –Duplicated chromosomes are evenly distributed into two daughter nuclei

51. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.6 Cell division is a continuum of dynamic changes In mitosis, after the chromosomes coil up –A mitotic spindle moves them to the middle of the cell

52. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The sister chromatids then separate –And move to opposite poles of the cell, where two nuclei form Cytokinesis, in which the cell divides in two –Overlaps the end of mitosis

53. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The stages of cell division INTERPHASEPROPHASEPROMETAPHASE LM 250  Chromatin Centrosomes (with centriole pairs) Nucleolus Nuclear envelope Plasma membrane Early mitotic spindle Centrosome Centromere Chromosome, consisting ot two sister chromatids Spindle microtubules Kinetochore Fragments of nuclear envelope Figure 8.6 (Part 1)

54. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Spindle Metaphase plate Daughter chromosomes Nuclear envelope forming Cleavage furrow Nucleolus forming Figure 8.6 (Part 2)

55. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.7 Cytokinesis differs for plant and animal cells In animals –Cytokinesis occurs by a constriction of the cell (cleavage) Cleavage furrow SEM 140  Daughter cells Cleavage furrow Contracting ring of microfilaments Figure 8.7A

56. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings In plants –A membranous cell plate splits the cell in two Figure 8.7B TEM 7,500  Cell plate forming Wall of parent cell Daughter nucleus Cell wall New cell wall Vesicles containing cell wall material Cell plate Daughter cells

57. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.8 Anchorage, cell density, and chemical growth factors affect cell division Most animal cells divide –Only when stimulated, and some not at all

58. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Cells anchor to dish surface and divide. When cells have formed a complete single layer, they stop dividing (density- dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition). In laboratory cultures –Most normal cells divide only when attached to a surface They continue dividing –Until they touch one another Figure 8.8A

59. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Growth factors –Are proteins secreted by cells that stimulate other cells to divide After forming a single layer, cells have stopped dividing. Providing an additional supply of growth factors stimulates further cell division. Figure 8.8B

60. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.9 Growth factors signal the cell cycle control system A set of proteins within the cell –Controls the cell cycle

61. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Signals affecting critical checkpoints in the cell cycle –Determine whether a cell will go through the complete cycle and divide Control system G1G1 S G2G2 M G 1 checkpoint G 2 checkpoint M checkpoint G0G0 Figure 8.9A

62. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The binding of growth factors to specific receptors on the plasma membrane –Is usually necessary for cell division. Control system G1G1 S G2G2 M G 1 checkpoint Plasma membrane Growth factor Receptor protein Relay proteins Signal transduction pathway Figure 8.9B

63. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 8.10 Growing out of control, cancer cells produces malignant tumors Cancer cells –divide excessively to form masses called tumors

64. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Malignant tumors –Can invade other tissues Tumor Glandular tissue A tumor grows from a single cancer cell. Cancer cells invade neighboring tissue. Cancer cells spread through lymph and blood vessels to other parts of the body. Lymph vessels Blood vessel Figure 8.10

65. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Radiation and chemotherapy –Are effective as cancer treatments because they interfere with cell division

66. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8.11 Review of the functions of mitosis: Growth, cell replacement, and asexual reproduction When the cell cycle operates normally, mitotic cell division functions in –Growth LM 500  Figure 8.11A

67. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings LM 700  Replacement of damaged or lost cells Figure 8.11B

68. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Asexual reproduction LM 10  Figure 8.11C