1. Cell Growth & Division: Meiosis
Chapter 11
Cell Growth & Division: Meiosis

2. Cell Growth & Division: Meiosis
I. Meiosis
Nuclear division that produces sex cells /gametes
In REPRODUCTIVE ORGANS only
2 divisions: Meiosis I & Meiosis II
Cell Growth & Division: Meiosis

3. Cell Growth & Division: Meiosis
II. Stages
PROPHASE I
1. centrioles & spindle fibers appear
2. nuclear mem. & nucleolus disappear
Cell Growth & Division: Meiosis

4. Cell Growth & Division: Meiosis
3. Crossing over= exchange of genetic material between
Between homologous chromosomes
Ensures genetic variation!
Tetrad formed
Cell Growth & Division: Meiosis

6. Cell Growth & Division: Meiosis
B. METAPHASE I
1. Chromosome PAIRS (homologous)line up in middle RANDOMLY
2. Ensures genetic variation!
3. Spindle fibers attach to centromeres
Cell Growth & Division: Meiosis

7. Cell Growth & Division: Meiosis
C. ANAPHASE I
1. Chromosome PAIRS (homologous) SEPARATE to opposite sides
Cell Growth & Division: Meiosis

8. Cell Growth & Division: Meiosis
D. TELOPHASE I
1. Nuclear membrane forms around chromosomes (temporarily).
2. Spindle fibers & centrioles disappear.
3. Cytokinesis occurs.
Cell Growth & Division: Meiosis

9. NO INTERPHASE!! What does that mean?
Well, there is NO DNA duplication.
Cells start with 46 chromosomes before being divided again.
Cell will have LESS than 46 chromosomes by the end of meiosis.
Wow.

10. Cell Growth & Division: Meiosis
E. PROPHASE II
1. Spindle fibers reappear. 2. Nuclear membrane disappears. 3. Starts with 46 chromosomes.
Cell Growth & Division: Meiosis

11. Cell Growth & Division: Meiosis
F. METAPHASE II
1. Chromosomes line up in middle.
2. Spindle fibers attach to centromeres.
Cell Growth & Division: Meiosis

12. Cell Growth & Division: Meiosis
G. ANAPHASE II
1. Chromosomes separate into chromatids & move to opposite ends.
Cell Growth & Division: Meiosis

13. Cell Growth & Division: Meiosis
H. TELOPHASE II
1. Spindle fibers & centrioles disappear. 2. Nuclear mem. & nucleolus reappear. 3. Cytokinesis follows.
Cell Growth & Division: Meiosis

14. Cell Growth & Division: Meiosis
I. CYTOKINESIS
1. Four non-identical cells – Back in interphase
Cell Growth & Division: Meiosis

15. Cell Growth & Division: Meiosis
III. MITOSIS VS. MEIOSIS
Cell Growth & Division: Meiosis
Mitosis
Meiosis
2 IDENTICAL cells
4 NON-IDENTICAL cells
Start =46 chr. End = 46 chr.
Start =46 chr. End = 23 chr.
Cell Growth & Division: Meiosis

16. Cell Growth & Division: Meiosis
Mitosis
Meiosis
No crossing over
Crossing over in Prophase I
Makes BODY cells
Makes SEX cells
Cell Growth & Division: Meiosis

17. Cell Growth & Division: Meiosis
Body Cells
Sex Cells
Sci. name = SOMATIC cells
Sci. name = GAMETES
DIPLOID
HAPLOID
46 chr. (23 pairs)
23 chr. (unpaired)
Cell Growth & Division: Meiosis

18. IV. Miscellaneous Meiosis
Cell Growth & Division: Meiosis
IV. Miscellaneous Meiosis
Meiosis in males:
SPERMATOGENESIS
makes 4 sperm cells
B. Meiosis in females: OOGENESIS
makes only 1 mature egg (ovum)
Cell Growth & Division: Meiosis

19. Cell Growth & Division: Meiosis
Why only 1 egg?
a. unequal division of cytoplasm in both telophase I & II
Cell Growth & Division: Meiosis

20. Cell Growth & Division: Meiosis
Cell Growth & Division: Meiosis

21. V. Asexual & Sexual Reproduction
Cell Growth & Division: Meiosis
V. Asexual & Sexual Reproduction
ASEXUAL reproduction = making of offspring from 1 parent
B. SEXUAL reproduction = making of offspring by combining gametes from 2 parents
Cell Growth & Division: Meiosis