1. CHAPTER 8 The Cellular Basis of Reproduction and Inheritance
Modules 8.1 – 8.3

2. How to Make a Sea Star — With and Without Sex
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

3. Some organisms can also reproduce asexually
This sea star is regenerating a lost arm
Regeneration results from repeated cell divisions

4. CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION
Cell division is at the heart of the reproduction of cells and organisms
Organisms can reproduce sexually or asexually

5. 8.1 Like begets like, more or less
Some organisms make exact copies of themselves, asexual reproduction
Figure 8.1A

6. Other organisms make similar copies of themselves in a more complex process, sexual reproduction
Figure 8.1B

7. 8.2 Cells arise only from preexisting cells
All cells come from cells
Cellular reproduction is called cell division
Cell division allows an embryo to develop into an adult
It also ensures the continuity of life from one generation to the next

8. 8.3 Prokaryotes reproduce by binary fission
Prokaryotic cells divide asexually
These cells possess a single chromosome, containing genes
The chromosome is replicated
The cell then divides into two cells, a process called binary fission
Prokaryotic chromosomes
Figure 8.3B

9. Binary fission of a prokaryotic cell
Plasma membrane
Prokaryotic chromosome
Cell wall
Duplication of chromosome and separation of copies
Continued growth of the cell and movement of copies
Division into two cells
Figure 8.3A

10. CHAPTER 8 The Cellular Basis of Reproduction and Inheritance
Modules 8.4 – 8.11

11. 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
The genes are grouped into multiple chromosomes, found in the nucleus
The chromosomes of this plant cell are stained dark purple
Figure 8.4A

12. Chromosomes contain a very long DNA molecule with thousands of genes
Individual chromosomes are only visible during cell division
They are packaged as chromatin

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

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

15. 8.5 The cell cycle multiplies cells
The cell cycle consists of two major phases:
Interphase, where chromosomes duplicate and cell parts are made
The mitotic phase, when cell division occurs
Figure 8.5

16. 8.6 Cell division is a continuum of dynamic changes
Eukaryotic cell division consists of two stages:
Mitosis
Cytokinesis

17. In mitosis, the duplicated chromosomes are distributed into two daughter nuclei
After the chromosomes coil up, a mitotic spindle moves them to the middle of the cell

18. Centrosomes (with centriole pairs) Early mitotic spindle Centrosome
INTERPHASE
PROPHASE
Centrosomes (with centriole pairs)
Early mitotic spindle
Centrosome
Fragments of nuclear envelope
Kinetochore
Chromatin
Centrosome
Spindle microtubules
Nucleolus
Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Figure 8.6

19. The sister chromatids then separate and move to opposite poles of the cell
The process of cytokinesis divides the cell into two genetically identical cells

20. TELOPHASE AND CYTOKINESIS
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
Cleavage furrow
Nucleolus forming
Metaphase plate
Nuclear envelope forming
Spindle
Daughter chromosomes
Figure 8.6 (continued)

21. 8.7 Cytokinesis differs for plant and animal cells
In animals, cytokinesis occurs by cleavage
This process pinches the cell apart
Cleavage furrow
Cleavage furrow
Contracting ring of microfilaments
Figure 8.7A
Daughter cells

22. In plants, a membranous cell plate splits the cell in two
Cell plate forming
Wall of parent cell
Daughter nucleus
In plants, a membranous cell plate splits the cell in two
Cell wall
New cell wall
Vesicles containing cell wall material
Cell plate
Daughter cells
Figure 8.7B

23. Most animal cells divide only when stimulated, and others not at all
8.8 Anchorage, cell density, and chemical growth factors affect cell division
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

24. Cells continue dividing until they touch one another
This is called density-dependent inhibition
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).
Figure 8.8A

25. 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

26. 8.9 Growth factors signal the cell cycle control system
Proteins within the cell control the cell cycle
Signals affecting critical checkpoints determine whether the cell will go through a complete cycle and divide
G1 checkpoint
Control system
M checkpoint
G2 checkpoint
Figure 8.9A

27. Cell cycle control system
The binding of growth factors to specific receptors on the plasma membrane is usually necessary for cell division
Growth factor
Plasma membrane
Relay proteins
Receptor
protein
G1 checkpoint
Signal transduction pathway
Cell cycle control system
Figure 8.8B

28. Cancer cells have abnormal cell cycles
8.10 Connection: Growing out of control, cancer cells produce malignant tumors
Cancer cells have abnormal cell cycles
They divide excessively and can form abnormal masses called tumors
Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division

29. Malignant tumors can invade other tissues and may kill the organism
Lymph vessels
Tumor
Glandular tissue
Metastasis 1
A tumor grows from a single cancer cell. 2
Cancer cells invade neighboring tissue. 3
Cancer cells spread through lymph and blood vessels to other parts of the body.
Figure 8.10

30. 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 (seen here in an onion root)
Figure 8.11A

31. Cell replacement (seen here in skin)
Dead cells
Epidermis, the outer layer of the skin
Dividing cells
Dermis
Figure 8.11B

32. Asexual reproduction (seen here in a hydra)
Figure 8.11C

33. CHAPTER 8 The Cellular Basis of Reproduction and Inheritance
Modules 8.12 – 8.18

34. 8.12 Chromosomes are matched in homologous pairs
MEIOSIS AND CROSSING OVER
8.12 Chromosomes are matched in homologous pairs
Somatic cells of each species contain a specific number of chromosomes
Human cells have 46, making up 23 pairs of homologous chromosomes
Chromosomes
Centromere
Sister chromatids
Figure 8.12

35. 8.13 Gametes have a single set of chromosomes
Cells with two sets of chromosomes are said to be diploid
Gametes are haploid, with only one set of chromosomes

36. 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

37. Multicellular diploid adults (2n = 46) Mitosis and development
The human life cycle
Haploid gametes (n = 23)
Egg cell
Sperm cell
MEIOSIS
FERTILIZATION
Diploid zygote (2n = 46)
Multicellular diploid adults (2n = 46)
Mitosis and development
Figure 8.13

38. 8.14 Meiosis reduces the chromosome number from diploid to haploid
Meiosis, like mitosis, is preceded by chromosome duplication
However, in meiosis the cell divides twice to form four daughter cells

39. In the first division, meiosis I, homologous chromosomes are paired
While they are paired, they cross over and exchange genetic information
The homologous pairs are then separated, and two daughter cells are produced

40. MEIOSIS I: Homologous chromosomes separate
INTERPHASE
PROPHASE I
METAPHASE I
ANAPHASE I
Centrosomes (with centriole pairs)
Microtubules attached to kinetochore
Sites of crossing over
Metaphase plate
Sister chromatids remain attached
Spindle
Nuclear envelope
Chromatin
Sister chromatids
Tetrad
Centromere (with kinetochore)
Homologous chromosomes separate
Figure 8.14, part 1

41. Meiosis II is essentially the same as mitosis
The sister chromatids of each chromosome separate
The result is four haploid daughter cells

42. MEIOSIS II: Sister chromatids separate
TELOPHASE I AND CYTOKINESIS
TELOPHASE II AND CYTOKINESIS
PROPHASE II
METAPHASE II
ANAPHASE II
Cleavage furrow
Sister chromatids separate
Haploid daughter cells forming
Figure 8.14, part 2

43. 8.15 Review: A comparison of mitosis and meiosis
For both processes, chromosomes replicate only once, during interphase

44. PARENT CELL (before chromosome replication) Site of crossing over
MITOSIS
MEIOSIS
PARENT CELL (before chromosome replication)
Site of crossing over
MEIOSIS I
PROPHASE
PROPHASE I
Tetrad formed by synapsis of
homologous chromosomes
Duplicated chromosome (two sister chromatids)
Chromosome replication
Chromosome replication
2n = 4
Chromosomes align at the metaphase plate
Tetrads align at the metaphase plate
METAPHASE
METAPHASE I
ANAPHASE I
TELOPHASE I
ANAPHASE TELOPHASE
Sister chromatids separate during anaphase
Homologous chromosomes separate during anaphase I; sister chromatids remain together
Haploid n = 2
Daughter cells of meiosis I 2n 2n
No further chromosomal replication; sister chromatids separate during anaphase II
MEIOSIS II
Daughter cells of mitosis n n n n
Daughter cells of meiosis II
Figure 8.15

45. Each chromosome of a homologous pair comes from a different parent
8.16 Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring
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

46. 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

47. Two equally probable arrangements of chromosomes at metaphase I
POSSIBILITY 1
POSSIBILITY 2
Two equally probable arrangements of chromosomes at metaphase I
Metaphase II
Gametes
Combination 1
Combination 2
Combination 3
Combination 4
Figure 8.16

48. 8.17 Homologous chromosomes carry different versions of genes
The differences between homologous chromosomes are based on the fact that they can carry different versions of a gene at corresponding loci

49. C E C E C E c e c e c e Coat-color genes Eye-color genes Brown Black
White
Pink
Tetrad in parent cell (homologous pair of duplicated chromosomes)
Chromosomes of the four gametes
Figure 8.17A, B

50. 8.18 Crossing over further increases genetic variability
Crossing over is the exchange of corresponding segments between two homologous chromosomes
Genetic recombination results from crossing over during prophase I of meiosis
This increases variation further

51. Tetrad
Chaisma
Centromere
Figure 8.18A

52. How crossing over leads to genetic recombination
Coat-color genes
Eye-color genes
How crossing over leads to genetic recombination
Tetrad (homologous pair of chromosomes in synapsis) 1
Breakage of homologous chromatids 2
Joining of homologous chromatids
Chiasma
Separation of homologous chromosomes at anaphase I 3
Separation of chromatids at anaphase II and completion of meiosis 4
Parental type of chromosome
Recombinant chromosome
Recombinant chromosome
Parental type of chromosome
Figure 8.18B
Gametes of four genetic types

53. CHAPTER 8 The Cellular Basis of Reproduction and Inheritance
Modules 8.19 – 8.23

54. ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE
8.19 A karyotype is a photographic inventory of an individual’s chromosomes
To study human chromosomes microscopically, researchers stain and display them as a karyotype
A karyotype usually shows 22 pairs of autosomes and one pair of sex chromosomes

55. Preparation of a karyotype
Fixative
Packed red
And white
blood cells
Hypotonic solution
Blood culture
Stain
White
Blood cells
Centrifuge 3 2 1
Fluid
Centromere
Sister chromatids
Pair of homologous chromosomes 4 5
Figure 8.19

56. 8.20 Connection: An extra copy of chromosome 21 causes Down syndrome
This karyotype shows three number 21 chromosomes
An extra copy of chromosome 21 causes Down syndrome
Figure 8.20A, B

57. The chance of having a Down syndrome child goes up with maternal age
Figure 8.20C

58. 8.21 Accidents during meiosis can alter chromosome number
Abnormal chromosome count is a result of nondisjunction
Either homologous pairs fail to separate during meiosis I
Nondisjunction in meiosis I
Normal meiosis II
Gametes
n + 1
n + 1
n – 1
n – 1
Number of chromosomes
Figure 8.21A

59. Or sister chromatids fail to separate during meiosis II
Normal meiosis I
Nondisjunction in meiosis II
Gametes
n + 1
n – 1 n n
Number of chromosomes
Figure 8.21B

60. Fertilization after nondisjunction in the mother results in a zygote with an extra chromosome
Egg cell
n + 1
Zygote 2n + 1
Sperm cell
n (normal)
Figure 8.21C

61. 8.22 Connection: Abnormal numbers of sex chromosomes do not usually affect survival
Nondisjunction can also produce gametes with extra or missing sex chromosomes
Unusual numbers of sex chromosomes upset the genetic balance less than an unusual number of autosomes

62. Table 8.22

63. A man with Klinefelter syndrome has an extra X chromosome
Poor beard growth
Breast development
Under- developed testes
Figure 8.22A

64. A woman with Turner syndrome lacks an X chromosome
Characteristic facial features
Web of skin
Constriction of aorta
Poor breast development
Under- developed
ovaries
Figure 8.22B

65. 8.23 Connection: Alterations of chromosome structure can cause birth defects and cancer
Chromosome breakage can lead to rearrangements that can produce genetic disorders or cancer
Four types of rearrangement are deletion, duplication, inversion, and translocation

66. Homologous chromosomes
Deletion
Duplication
Homologous chromosomes
Inversion
Reciprocal translocation
Nonhomologous chromosomes
Figure 8.23A, B

67. Chromosomal changes in a somatic cell can cause cancer
A chromosomal translocation in the bone marrow is associated with chronic myelogenous leukemia
Chromosome 9
Reciprocal translocation
Chromosome 22
“Philadelphia chromosome”
Activated cancer-causing gene
Figure 8.23C

68. CHAPTER 8 Extra Photographs

69. Sea urchin development
Figure 8.0x

70. E. coli dividing
Figure 8.3x

71. Cell cycle collage
Figure 8.5x

72. Mitosis collage, light micrographs
Figure 8.6x1

73. Mitotic spindle
Figure 8.6x2

74. Fibroblast growth
Figure 8.8x

75. Breast cancer cell
Figure 8.10x1

76. Mammograms
Figure 8.10x2

77. Human female bands
Figure 8.19x1

78. Human female karyotype
Figure 8.19x2

79. Human male bands
Figure 8.19x3

80. Human male karyotype
Figure 8.19x4

81. Down syndrome karyotype
Figure 8.20Ax

82. Klinefelter’s karyotype
Figure 8.22Ax

83. XYY karyotype
Figure 8.22x

84. Translocation
Figure 8.23Bx