1. Cellular Reproduction
Cell Division
cellular material is divided between new daughter cells
Nuclear division: Mitosis or Meiosis
Cytoplasmic division: Cytokinesis

2. Mitosis and Meiosis in the Human Life Cycle
2n = diploid = 2 sets of chromosomes
n = haploid = 1 set of chromosomes

3. Cell Cycle with MitosisP M
Mitosis
P = prophase
M = metaphase
A = anaphase
T = telophase A G2 T
assembly of
components
for division
cytokinesis
Interphase
G1 = growth phase 1
S = synthesis phase
G2 = growth phase 2 S G1
cytoplasm
doubles
chromosomes
replicate
Interphase

4. Applying Your KnowledgeS G2
Mitosis
Cytokinesis
When does nuclear division occur?
When are the chromosomes duplicated?
When do the cytoplasmic contents double?

5. Interphase nucleus nucleolus
Chromatin is diffuse, individual chromosomes cannot be distinguished.

6. Prophase Chromosomes condense. Spindle forms. Nucleolus disappears.
Nuclear envelope breaks down.

7. centromere
chromatid
chromatid
Sister
Chromatids are held together at their centromeres.
Each chromosome appears as a pair of chromatids attached at the centromere.

8. Metaphase
Chromatid pairs align at the cell equator.

10. Anaphase
Sister chromatids separate and are drawn to opposite poles by spindle fibers.

11. Telophase Chromosomes have reached poles of cell. Spindle disperses.
Nuclear envelope surrounds chromosomes.
Chromosomes become diffuse, nucleolus reforms.

12. Telophase + Cytokinesis
New Daughter Cells
These phases can overlap in time.

13. Cytokinesis in animal cells
Cytokinesis in plant cells

14. Applying Your Knowledge
Prophase
Metaphase
Anaphase
Telophase
When do chromosomes line up at the cell equator?
When are sister chromatids first visible?
When do sister chromatids separate from each other?

15. Outcome of Meiotic Divisions
Human Cell with 46 chromosomes (Diploid)
Duplication of Cell Contents
Two Chromosomal Divisions (Meiosis I and Meiosis II)
4 Genetically-Different Human Cells , Each with 23 chromosomes (Haploid)

16. Homologous Chromosome Pairs
Diploid cells have pairs of chromosomes
Each homologous chromosome pair is genetically matched so that the genes are arranged in the same order
Figure: 11.UN06b
Title:
Formation of daughter chromosomes
Caption:

17. Cell Cycle With Meiosis
M1 = meiosis I
M2 = meiosis II M1 G2 M2
assembly of
components
for division
cytokinesis S G1
Interphase
G1 = growth phase 1
S = synthesis phase
G2 = growth phase 2
cytoplasm
doubles
chromosomes
replicate
Interphase

18. Applying Your Knowledge
G1 phase
S phase
G2 phase
Meiosis I and II
When does chromosome duplication occur?
When do the cytoplasmic contents double?
When does chromosomal division occur?

19. Meiotic Divisions Meiosis I: reduction division
Separation of homologous chromosomes into two different nuclei
Chromosome number reduced to haploid
Meiosis II: equational division
Duplicated chromosomes separate
No change in chromosome number

20. Phases of Meiosis I Prophase I Metaphase I Anaphase I Telophase I
--Chromosomes Shorten and Thicken (condense) --Homologous Chromosomes Pair with Each Other and Exchange Genetic Information
Metaphase I
Chromosome Pairs Line up at Cell Equator
Anaphase I
Homologous Chromosomes Separate
Telophase I
Separated Homologues Reach Opposite Poles

21. Centromeres
Chromatid (duplicate)
Non-sister chromatids
Chromosomes condense.
Synapsis (pairing) of homologs occurs.
Crossing-over occurs at chiasma (contact points).

22. Crossing Over Homologous Pairs Exchange Genetic Information
Figure: 11.15
Title:
The mechanism of crossing over
Caption:
1) Homologous chromosomes pair up side by side. 2) One end of each chromosome binds to the nuclear envelope. Protein strands “zip” homologous chromosomes together. 3) Homologous chromosomes are fully joined by protein strands. 4) Recombination enzymes bind to the chromosomes. Recombination enzymes snip chromatids apart and reattach the chromatids. Chiasmata are formed when one end of a chromatid of a paternal chromosome (yellow) is attached to the other end of a chromatid of a maternal chromosome (violet). 5) The protein strands and recombination enzymes leave as the chromosomes condense. The chiasmata remain as locations where homologous chromosomes are twisted around each other, helping to hold homologues together.
Chromosomes
with combinations of maternal and paternal traits

23. Chromosome pairs align at the center of the spindle.
Homologues move to opposite poles of the cell. I

24. Cytokinesis along the central plane yields two haploid cells with duplicated chromosomes.
Prior to the start of Meiosis II, there may be a pause called interkinesis but the chromosomes do not duplicate a second time.
Homologues reach opposite poles.

25. Phases of Meiosis II Prophase II Metaphase II Anaphase II Telophase II
--Chromosomes Shorten and Thicken (condense)
--No Chromosome Pairing Occurs
Metaphase II
Chromosomes Line up at Cell Equator
Anaphase II
Sister Chromatids Separate
Telophase II
Separated Chromosomes Reach Opposite Poles

26. Chromosomes condense.
Chromosomes align at the cell equators on the new spindles.
Sister chromatids separate at centromeres and move to
opposite poles.

27. Daughter chromosomes reach opposite poles.
After cytokinesis, four genetically-different
haploid cells are formed.

28. Sperm formation
Equal divisions of cytoplasm
Four functional products per meiosis
Egg formation
Unequal divisions of cytoplasm
Small polar bodies formed
One functional product per meiosis

29. Applying Your Knowledge
Prophase I
Metaphase I
Anaphase I
Metaphase II
Anaphase II
When do sister chromatids separate?
When does crossing over occur?
When do homologous pairs line up at the cell equator?

30. Comparing Mitosis and Meiosis
Cell type at start
Cell type at end
Are products identical? (Y/N)
Number of cells produced
Number of chromosome duplications
Pairing of homologues (Y/N)
Crossing-over (Y/N)
Number of chromosome divisions

31. Comparing Mitosis and Meiosis
Cell type at start
Diploid
Cell type at end
Haploid
Are products identical? (Y/N)
Yes No
Number of cells produced
Two
Four
Number of chromosome duplications prior to
One
Pairing of homologues (Y/N)
Crossing-over (Y/N)
Number of chromosome divisions