1. BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 8 The Cellular Basis of Reproduction and Inheritance Modules 8.1 – 8.3

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The life cycle of a multicellular organism includes –development –reproduction This sea star embryo (morula) shows one stage in the development of a fertilized egg –The cluster of cells will continue to divide as development proceeds How to Make a Sea Star — With and Without Sex

3. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some organisms can also reproduce asexually –This sea star is regenerating a lost arm –Regeneration results from repeated cell divisions

4. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Reproduction is one phase of an organism's life cycle 1.Sexual reproduction= Fertilization of sperm and egg produces offspring 2. Asexual reproduction= Offspring are produced by a single parent, without the participation of sperm and egg

5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell division is at the heart of the reproduction of cells and organisms –Asexual reproduction Chromosomes are duplicated and cell divides Each daughter cell is genetically identical to the parent and the other daughter –Sexual reproduction Each offspring inherits a unique combination of genes from both parents Offspring can show great variation CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION

6. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some organisms make exact copies of themselves; reproduction from a single parent is asexual reproduction 8.1 Like begets like, more or less Figure 8.1A

7. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Other organisms make similar copies of themselves in a more complex process, sexual reproduction Figure 8.1B

8. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –"Every cell from a cell" is at the heart of the perpetuation of life Can reproduce an entire unicellular organism Is the basis of sperm and egg formation Allows for development from a single fertilized egg to an adult organism Functions in an organism's renewal and repair 8.2 Cells arise only from preexisting cells

9. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –binary fission= asexual Genes are on one circular DNA molecule The cell replicates its single chromosome The chromosome copies move apart The cell elongates The plasma membrane grows inward, dividing the parent into two daughter cells 8.3 Prokaryotes reproduce by binary fission Figure 8.3B Prokaryotic chromosomes

10. Continued elongation of the cell and movement of copies Duplication of chromosome and separation of copies Plasma membrane Cell wall Prokaryotic chromosome Division into two daughter cells Prokaryotic binary fission

11. 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

12. –Eukaryotic genes Many more than in prokaryotes Grouped into multiple chromosomes in the nucleus 8.4 The large, complex chromosomes of eukaryotes duplicate with each cell division THE EUKARYOTIC CELL CYCLE AND MITOSIS

13. Eukaryotic chromosomes – Contain a very long DNA molecule associated with proteins – Most of the time occur in the form of thin, loosely packed chromatin fibers – Condense into visible chromosomes just before cell division – Individual chromosomes are only visible during cell division

15. Before a cell starts dividing, the chromosomes are duplicated –This process produces sister chromatids Centromere Sister chromatids Figure 8.4B

16. When the cell divides, the sister chromatids separate –Two daughter cells are produced –Each has a complete and identical set of chromosomes Centromere Sister chromatids Figure 8.4C Chromosome duplication Chromosome distribution to daughter cells

17. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings - Eukaryotic cell cycle divided into two phases Interphase= Acquisition of nutrients, growth, chromosome duplication Cell division= One copy of every chromosome and half of cytoplasm and organelles parceled out into two daughter cells 8.5 The cell cycle multiplies cells Figure 8.5

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19. –The cell actually divides in mitotic (M) phase Mitosis: nuclear division Cytokinesis: cytoplasmic division Duplicated chromosomes evenly distributed into two daughter nuclei 8.6 Cell division is a continuum of dynamic changes

20. Duplication of the genetic material ends when chromosomes begin to become visible

21. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The mitotic spindle is forming. Centrosomes migrate to opposite ends of the cell

22. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chromatins completely coil into chromosomes; nucleoli and nuclear membrane disperse

23. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The spindle is fully formed; chromosomes are aligned single file with centromeres on the metaphase plate

24. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chromosomes separate from the centromere, dividing to arrive at poles

25. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell elongation continues, a nuclear envelope forms around chromosomes, chromosomes uncoil, and nucleoli reappear

26. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings INTERPHASEPROPHASE Centrosomes (with centriole pairs) Chromatin NucleolusNuclear envelope Plasma membrane Early mitotic spindle Centrosome Centromere Chromosome, consisting of two sister chromatids Fragments of nuclear envelope Kinetochore Spindle microtubules Figure 8.6

27. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings METAPHASETELOPHASE AND CYTOKINESIS Metaphase plate SpindleDaughter chromosomes Cleavage furrow Nucleolus forming Nuclear envelope forming ANAPHASE Figure 8.6 (continued)

28. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In animals, cytokinesis occurs by cleavage –This process pinches the cell apart 8.7 Cytokinesis differs for plant and animal cells Figure 8.7A Cleavage furrow Contracting ring of microfilaments Daughter cells

29. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In plants, a membranous cell plate splits the cell in two Vesicles containing cell wall material Cell plate forming Figure 8.7B Cell plateDaughter cells Wall of parent cell Daughter nucleus Cell wallNew cell wall

30. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most animal cells divide only when stimulated, and others not at all In laboratory cultures, most normal cells divide only when attached to a surface –They are anchorage dependent 8.8 Anchorage, cell density, and chemical growth factors affect cell division

31. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cells continue dividing until they touch one another –This is called density-dependent inhibition Cells anchor to dish surface and divide. Figure 8.8A 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).

32. Copyright © 2003 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. Figure 8.8B Providing an additional supply of growth factors stimulates further cell division.

33. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Proteins within the cell control the cell cycle –Signals affecting critical checkpoints determine whether the cell will go through a complete cycle and divide 8.9 Growth factors signal the cell cycle control system

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35. The binding of growth factors to specific receptors on the plasma membrane is usually necessary for cell division Growth factor Figure 8.8B Cell cycle control system Plasma membrane Receptor protein Signal transduction pathway G 1 checkpoint Relay proteins

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION Cancer cells do not respond normally to the cell cycle control system – Divide excessively – Can invade other tissues – May kill the organism 8.10 Connection: Growing out of control, cancer cells produce malignant tumors

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings If an abnormal cell avoids destruction by the immune system, it may form a tumor – Benign: abnormal cells remain at original site – Malignant: abnormal cells can spread to other tissues and parts of the body – Metastasis: spread of cancer cells through the circulatory system

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cancers are named according to location of origin – Carcinoma: external or internal body coverings – Sarcoma: tissues that support the body – Leukemia and lymphoma: blood-forming tissues Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division

39. LE 8-10 Tumor Glandular tissue Lymph vessels Blood vessel 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. Malignant tumors can invade other tissues and may kill the organism

40. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings When the cell cycle operates normally, mitotic cell division functions in: –Growth (seen here in an onion root) 8.11 Review of the functions of mitosis: Growth, cell replacement, and asexual reproduction Figure 8.11A

41. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell replacement (seen here in skin) Dead cells Figure 8.11B Dividing cells Epidermis, the outer layer of the skin Dermis

42. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Asexual reproduction (seen here in a hydra) Figure 8.11C

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 8.12 Chromosomes are matched in homologous pairs MEIOSIS AND CROSSING OVER The somatic (body) cells of each species contain a specific number of chromosomes Humans and most other organisms have pairs of homologous chromosomes. Human cells have 46, making up 23 pairs of homologous chromosomes – Carry genes for the same characteristics at the same place, or locus Except sex chromosomes – One chromosome is inherited from the female parent, one from the male

44. Homologous Pairs of Chromosomes Chart showing entire set of stained chromosomes (karyotype) shows pairs –Every chromosome in a non-reproductive cell has a “partner” or homologous chromosome –Homologues contain the same kinds of genes and have the same size, shape, and banding pattern

45. LE 8-12 Chromosomes Centromere Sister chromatids

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Diploid cells have two sets of chromosomes (2n) – Somatic cells Haploid cells have one set of chromosomes (n) – Gametes (egg and sperm cells) 8.13 Gametes have a single set of chromosomes

48. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sexual life cycles involve the alternation of haploid and diploid stage At fertilization, a sperm fuses with an egg, forming a diploid zygote –Repeated mitotic divisions lead to the development of a mature adult –The adult makes haploid gametes by meiosis –All of these processes make up the sexual life cycle of organisms

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50. LE 8-13 Haploid gametes (n  23) Egg cell Sperm cell FertilizationMeiosis Diploid zygote (2n  46) n Multicellular diploid adults (2n  46) Mitosis and development 2n n

51. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Meiosis Like mitosis, is preceded by chromosome duplication Unlike mitosis, cell divides twice to form four haploid daughter cells 8.14 Meiosis reduces the chromosome number from diploid to haploid

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The process of meiosis includes two consecutive divisions – Meiosis I In synapsis, homologous chromosomes are paired In crossing over, homologous chromosomes exchange corresponding segments Each homologous pair divides into two daughter cells, each with one set of chromosomes consisting of two chromatids

53. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.14, part 1 MEIOSIS I : Homologous chromosomes separate INTERPHASEPROPHASE I METAPHASE I ANAPHASE I Centrosomes (with centriole pairs) Nuclear envelope Chromatin Sites of crossing over Spindle Sister chromatids Tetrad Microtubules attached to kinetochore Metaphase plate Centromere (with kinetochore) Sister chromatids remain attached Homologous chromosomes separate

54. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.14, part 2 MEIOSIS II : Sister chromatids separate TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II Cleavage furrow Sister chromatids separate TELOPHASE II AND CYTOKINESIS Haploid daughter cells forming

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis II – Essentially the same as mitosis – Sister chromatids of each chromosome separate – Result is four haploid cells, each with half as many chromosomes as the parent

56. LE 8-14a I NTERPHASE P ROPHASE  M ETAPHASE  A NAPHASE  M EIOSIS  Centrosomes (with centriole pairs) Sites of crossing over Spindle Microtubules attached to kinetochore Metaphase plate Sister chromatids remain attached Homologous chromosomes separate Centromere (with kinetochore) Tetrad Sister chromatids Chromatin Nuclear envelope : Homologous chromosome separate

57. LE 8-14b Cleavage furrow T ELOPHASE  P ROPHASE  M ETAPHASE  A NAPHASE  T ELOPHASE  Sister chromatids separate Haploid daughter cells forming M EIOSIS  : Sister chromatids separate  AND C YTOKINESIS

58. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings For both processes, chromosomes replicate only once, during interphase –Mitosis Provides for growth, tissue repair, and asexual reproduction Produces daughter cells genetically identical to the parent –Meiosis Needed for sexual reproduction Produces daughter cells with one member of each homologous chromosome pair 8.15 Review: A comparison of mitosis and meiosis

59. LE 8-15 M ITOSIS M EIOSIS M EIOSIS  M EIOSIS  Prophase Duplicated chromosome (two sister chromatids) Metaphase Anaphase Telophase Parent cell (before chromosome replication) Chromosomes align at the metaphase plate Sister chromatids separate during anaphase Daughter cells of mitosis 2n2n 2n2n n 2n  4 Chromosome replication Chromosome replication Tetrads align at the metaphase plate Homologous chromosomes separate during anaphase  ; sister chromatids remain together No further chromosomal replication; sister chromatids separate during anaphase  nn Daughter cells of meiosis  Daughter cells of meiosis  Site of crossing over Tetrad formed by synapsis of homologous chromosomes Prophase  Metaphase  Anaphase  Telophase  Haploid n  2 n

60. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Each chromosome of a homologous pair comes from a different parent –Each chromosome thus differs at many points from the other member of the pair 8.16 Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring

61. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The large number of possible arrangements of chromosome pairs at metaphase I of meiosis leads to many different combinations of chromosomes in gametes Random fertilization also increases variation in offspring

62. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.16 POSSIBILITY 1POSSIBILITY 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Gametes Combination 1Combination 2Combination 3Combination 4

63. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Each chromosome of a homologous pair can bear different versions of genes at corresponding loci – Makes gametes (and thus offspring) different from one another – Examples: coat color and eye color in mice 8.17 Homologous chromosomes carry different versions of genes

64. LE 8-17b Brown coat (C); black eyes (E)White coat (c); pink eyes (e)

65. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.17A, B Coat-color genesEye-color genes BrownBlack CE ce WhitePink CE ce CE ce Tetrad in parent cell (homologous pair of duplicated chromosomes) Chromosomes of the four gametes

66. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Crossing over is a genetic rearrangement between two homologous chromosomes Homologues pair up into a tetrad during prophase I of meiosis Maternal and paternal chromatids break at the same place The two broken chromatids join together in a new way at the chiasma 8.18 Crossing over further increases genetic variability

67. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – When homologous chromosomes separate at anaphase I, each contains a new segment – In meiosis II, each sister chromatid goes to a different gamete – Gametes of four genetic types result

68. LE 8-18a Tetrad Chiasma Centromere TEM 2,200 

69. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings How crossing over leads to genetic recombination Figure 8.18B Tetrad (homologous pair of chromosomes in synapsis) Breakage of homologous chromatids Joining of homologous chromatids Chiasma Separation of homologous chromosomes at anaphase I Separation of chromatids at anaphase II and completion of meiosis Parental type of chromosome Recombinant chromosome Parental type of chromosome Gametes of four genetic types 1 2 3 4 Coat-color genes Eye-color genes

70. ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE 8.19 A karyotype is a photographic inventory of an individual's chromosomes A blood sample is treated with a chemical that stimulates mitosis After several days, another chemical arrests mitosis at anaphase, when chromosomes are most highly condensed Chromosomes are photographed and electronically arranged by size and shape into the karyotype Normal humans have 22 pairs of autosomes and two sex chromosomes Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

71. LE 8-19 Packed red and white blood cells Hypotonic solution Centrifuge Blood culture Fluid Fixative White blood cells Stain Centromere Sister chromatids Pair of homologous chromosomes 2,600 

72. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION 8.20 An extra copy of chromosome 21 causes Down syndrome A person may have an abnormal number of chromosomes Down syndrome is caused by trisomy 21, an extra copy of chromosome 21 – The most common human chromosome number abnormality – Many physical and mental problems – Increased incidence in older mothers

75. LE 8-20c Infants with Down syndrome (per 1,000 births) Age of mother 20253035 4045 50 10 20 30 40 50 60 70 80 90 0

76. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

77. LE 8-21a Number of chromosomes Gametes Normal meiosis  Normal meiosis  Nondisjunction in meiosis  n  1 n  1

78. LE 8-21b Number of chromosomes Gametes Normal meiosis  Nondisjunction in meiosis  n  1 n  1 n n

79. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fertilization of an egg resulting from nondisjunction with a normal sperm results in a zygote with an abnormal chromosome number – May be involved in trisomy 21

80. LE 8-21c Egg cell Sperm cell n (normal) n  1 Zygote 2n  1

81. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION 8.22 Abnormal numbers of sex chromosomes do not usually affect survival Nondisjunction can produce gametes with extra or missing sex chromosomes – Upset the genetic balance less than unusual numbers of autosomes – Lead to varying degrees of malfunction in humans – Usually do not affect survival

83. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 8.23 Alterations of chromosome structure can cause birth defects and cancer Breakage can lead to rearrangements affecting genes on one chromosome – Deletion: loss of a fragment of chromosome – Duplication: addition of a fragment to sister chromatid – Inversion: reattachment of a fragment in reverse order – Inversions least harmful because all genes are present in normal number

84. LE 8-23a Deletion Duplication Inversion Homologous chromosomes

85. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Translocation is the attachment of a chromosomal fragment to a nonhomologous chromosome – Can be reciprocal – May or may not be harmful

86. LE 8-23b

87. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chromosomal changes in sperm or egg cells can cause congenital disorders Chromosomal changes in a somatic cell may contribute to the development of cancer

88. LE 8-23c Reciprocal translocation “Philadelphia chromosome” Activated cancer-causing gene Chromosome 22 Chromosome 9