1. CELL DIVISION MITOSIS: Reproducing the nucleus of a somatic cell.
MEIOSIS:
Producing sex cells (gametes).
CYTOKINESIS:
Division of cytoplasm and organelles.

2. Both mitosis and meiosis consist of a sequence of phases:
MITOSIS & MEIOSIS, con’t.
Both mitosis and meiosis consist of a sequence of phases:
interphase (preparation for division)
prophase
metaphase
anaphase
telophase

3. Result of Mitosis: formation of two daughter nuclei
MITOSIS & MEIOSIS, con’t.
Result of Mitosis:
formation of two daughter nuclei
have the same chromosome number as original (parent) cell

4. Result of Meiosis: Concludes with cytokinesis
MITOSIS & MEIOSIS, con’t.
Result of Meiosis:
formation of 1 to 4 daughter nuclei
have half the chromosome number as original (parent) cell
Concludes with cytokinesis
division of the cytoplasm and organelles

5. A. Terminology 1. Chromatin 2. Chromosome
I. MITOSIS
A. Terminology
1. Chromatin
2. Chromosome
3. Diploid (46 or “2N” in humans)
4. Haploid (23 or “N” in humans)
5. Homologous chromosomes
6. Somatic cells

6. MITOSIS, con’t. B. PHASES: arbitrarily assigned 1. INTERPHASE:
a. NO division. Cell appears to be “resting”
b. the metabolic phase of the cell

7. d. Nucleus, nuclear membrane, nucleolus visible
Interphase, continued …
c. Chromatin visible
d. Nucleus, nuclear membrane, nucleolus visible
e. Centrioles located at poles
f. Longest phase
1. ~96% of the cell’s life cycle
2. average of 23/24 hours

8. Interphase of Mitosis
1. Interphase (25)

9. a. Centrioles move to opposite poles of cell
MITOSIS, con’t.
2. Prophase
a. Centrioles move to opposite poles of cell
b. Chromatin condenses into chromosomes
c. Nucleoli disappear
d. Spindle apparatus is organized

10. Late Prophase of Mitosis

11. f. Phase ends as spindle fibers attach to centromeres
MITOSIS, con’t.: Prophase
e. Toward end of phase, nuclear membrane dissipates
f. Phase ends as spindle fibers attach to centromeres
g. Each chromosome now consists of two chromatids

12. Chromosome at Metaphase
A single metaphase chromosome with two chromatids
11. Micrograph of Chromosome

13. a. Chromosomes arranged around equatorial plate
MITOSIS, con’t.
3. Metaphase
a. Chromosomes arranged around equatorial plate
b. “Single file”
c. Two spindle fibers attached at each centromere

14. d. A relatively short phase e. Chromosomes easily counted (KARYOTYPE)
MITOSIS, con’t.: Metaphase
d. A relatively short phase
e. Chromosomes easily counted (KARYOTYPE)
f. Phase ends as chromatids separate
g. Centromere splits as DNA replication is completed

15. Metaphase of Mitosis
4. Metaphase (28)

16. a. Begins as chromatids separate
MITOSIS, con’t.
4. ANAPHASE
a. Begins as chromatids separate
b. Spindles move chromosomes to opposite poles
c. Polar spindles elongate cells
d. Phase ends when chromosomes have arrived at poles

17. Anaphase of Mitosis
6. Late Anaphase (30)

18. a. “Reverse” of prophase
MITOSIS, con’t.
5. Telophase
a. “Reverse” of prophase
b. Identical sister chromosomes have arrived at opposite poles
c. Nuclear membrane reassembles
d. Spindle apparatus dissipates
e. Nucleolus reassembles

19. f. Chromosomes relax  chromatin
MITOSIS, con’t.: Telophase
f. Chromosomes relax  chromatin
g. Centrioles replicate
h. Each chromosome consists of a single complete strand of DNA
i. Phase ends when nuclear membrane is completely reassembled

20. 9. Interphase (33)
Telophase of Mitosis

21. 1. Begins during anaphase
MITOSIS, con’t. …
C. CYTOKINESIS
1. Begins during anaphase
2. Completed during telophase
3. Result: two daughter cells
a. Genetically identical to parent cell
b. Contain ~1/2 the cytoplasm, organelles

22. An overview of Mitosis showing all stages
10. Mitosis, Nuclear Division (34)

23. II. MEIOSIS: A special case of mitosis
Occurs during maturation of sex cells (gametes)
Result: daughter nuclei receive one half the number of chromosomes of somatic cells
Makes sexual reproduction possible

24. II. MEIOSIS, con’t.
A. Terminology
1. Haploid: having a single set of chromosomes per individual or cell (N)
2. Diploid: having two full sets of chromosomes per individual or cell (2N)

25. a. Usually find sexual reproduction in diploid organisms
II. MEIOSIS, con’t.: Diploid
a. Usually find sexual reproduction in diploid organisms
b. Provides enormous adaptive advantages:
1. allows for population variations
2. Increases chances for survival

26. 3. Homologous chromosomes: a. Chromosomes that pair during meiosis
II. MEIOSIS, con’t.: Terminology
3. Homologous chromosomes: a. Chromosomes that pair during meiosis
b. Have the same morphology
c. Contain genes governing the same characteristics

27. 4. Allele: one of the two or more alternate forms of a gene
MEIOSIS, con’t.: Terminology
4. Allele: one of the two or more alternate forms of a gene
a. dominant, recessive, co-dominant
b. examples:
B = Brown hair (dominant)
b = blonde hair (recessive)
c. Different alleles arise by mutations

28. a. sequence of DNA nucleotides
MEIOSIS, con’t.: Terminology
5. Gene:
a. sequence of DNA nucleotides
b. unit of heredity transmitted in the chromosome
6. Chromosome: sequence of genes

29. II. MEIOSIS, con’t.: Terminology
7. One gene – One enzyme theory:
A gene is that part of a DNA molecule responsible for the synthesis of one enzyme (polypeptide)

30. B. Phases of Meiosis 1. Two “sets” of events 2. Same names as mitosis
II. MEIOSIS, con’t.:
B. Phases of Meiosis
1. Two “sets” of events
2. Same names as mitosis
3. Must indicate phase ‘I’ or ‘II’ I = Reductional Division II = Equational Division

31. C. Reductional Division 1. Interphase I: Like mitosis
II. MEIOSIS, con’t.:
C. Reductional Division
1. Interphase I: Like mitosis
2. Prophase I:
a. Long, complex
b. Three subdivisions

32. II. MEIOSIS, con’t.: Prophase I
1. Early: like mitosis
2. Middle: important
a. homologs pair
b. crossing over occurs
c. exchange of genetic info
d. called “tetrads”
3. Late: like mitosis

33. Prophase I of Meiosis
2. Meiosis I – Middle Prophase I - (38)

34. b. Homologous pairs align c. One spindle fiber/centromere
II. MEIOSIS, con’t.:
3. Metaphase I
a. Similar to mitosis
b. Homologous pairs align
c. One spindle fiber/centromere
d. Ends as one of each pair is pulled to opposite poles
e. NO DNA replication!!

35. b. Members of homologous pairs move to poles
II. MEIOSIS, con’t.:
4. Anaphase I
a. Similar to mitosis
b. Members of homologous pairs move to poles
c. Moved by spindle fibers

36. Anaphase II of Meiosis
3. Meiosis I – Early Anaphase I - (39)

37. a. Nuclear membrane reorganizes b. Chromosomes “relax”
II. MEIOSIS, con’t.:
5. Telophase I
a. Nuclear membrane reorganizes
b. Chromosomes “relax”
6. Cytokinesis: may not occur

38. Telophase I of Meiosis
5. Meiosis I – Telophase I - (41)

39. a. Nuclei are haploid (N) b. Chromosome number is reduced by one-half
II. MEIOSIS, con’t.:
7. End result
a. Nuclei are haploid (N)
b. Chromosome number is reduced by one-half

41. D. Equational Division: 1. Interphase II a. NO DNA replication!!
II. MEIOSIS, con’t.:
D. Equational Division:
1. Interphase II
a. NO DNA replication!!
b. “Coffee break” for nuclei
c. May not occur

42. Interphase II of Meiosis
6. Meiosis II – Interphase II - (42)
Interphase II of Meiosis

43. a. Chromosomes condense b. Spindle apparatus forms
II. MEIOSIS, con’t.:
2. Prophase II
a. Chromosomes condense
b. Spindle apparatus forms
c. Two fibers/centromere
d. Membrane dissipates e. Like mitosis

44. b. Chromosomes on equator c. Single file
II. MEIOSIS, con’t.:
3. Metaphase II
a. Like mitosis
b. Chromosomes on equator
c. Single file
d. Ends with centromere replication

45. Metaphase II of Meiosis
8. Meiosis II – Metaphase II - (44)
Metaphase II of Meiosis

46. a. Centromeres replicate b. Chromatids pulled to opposite poles
II. MEIOSIS, con’t.:
4. Anaphase II
a. Centromeres replicate
b. Chromatids pulled to opposite poles

47. 9. Meiosis II – Late Anaphase II - (45)
Anaphase II of Meiosis

48. b. Nucleolus reorganizes c. Chromosomes relax d. Centrioles replicate
II. MEIOSIS, con’t.:
5. Telophase II
a. Nuclear membranes
reorganize
b. Nucleolus reorganizes
c. Chromosomes relax
d. Centrioles replicate
e. Like mitosis

49. Telophase II of Meiosis
10. Meiosis II – Telophase II – (46)
Telophase II of Meiosis

51. a. Females: unequal division of cytoplasm -one ovum, 3 polar bodies
II. MEIOSIS, con’t.:
5. Cytokinesis occurs
6. Result:
a. Females: unequal division of cytoplasm
-one ovum, 3 polar bodies
b. Males: equal division of cytoplasm
-four spermatozoa

52. Telophase II of Meiosis: Four new cells
11. Meiosis II – Sperm Cell – (47)
Telophase II of Meiosis: Four new cells

53. a. Different from parent cell b. Different from each other c. Haploid
II. MEIOSIS, con’t.:
7. Cells produced are:
a. Different from parent cell
b. Different from each other
c. Haploid

54. Spermatogenesis
Spermatogenesis results in four spermatozoa

55. Oogenesis
Oogenesis results in one Ovum and two or three polar bodies