1. 11-4 Meiosis
Pg. 275

2. A. Purpose of Meiosis 1. Make reproductive cells (sex cells).
2. Reduces chromosome # in half.

3. B. Chromosome Number
1. The same type of chromosomes (male + female).

4. B. Chromosome Number
2. 2 sets of homologous chromosomes in cells = DIPLOID.
2N=46

5. B. Chromosome Number
3. Reproductive cells contain one set of chromosomes = HAPLOID
N=23

6. Practice!!! 1. Human cells- 2n=46 2. Human Cells- n= 23
Haploid or Diploid?
2. Human Cells- n= 23
Haploid or Diploid?

7. C. Phases of Meiosis

8. INTERPHASE
Chromosomes not visible.
Chromosomes are replicated.

9. Meiosis I: PROPHASE I Centrioles move apart.
Homologous chromosomes line up (tetrad).
Crossing over occurs.
Diploid

10. CROSSING OVER

11. Meiosis I: METAPHASE I Centrioles attach to spindle fiber.
Tetrads line up in the middle.
Diploid

12. Meiosis I: ANAPHASE I
Homologous chromosomes separate to opposite poles.
Diploid

13. Meiosis I: TELOPHASE I
The chromosomes uncoil, cytoplasm divide and spindle disappears.
Contains half the genetic material of original cell.
Diploid

14. Meiosis II: Prophase II
Centrioles move to opposite poles.
Spindle fibers begin to form.
Nucleolus disappears and nuclear envelope breaks apart.
Haploid

15. Meiosis II: METAPHASE II
Chromosomes line up in the middle.
Spindle fibers attach to the centromeres.
Haploid

16. Meiosis II: ANAPHASE II
Chromosomes split into sister chromatids.
Haploid

17. Meiosis II: TELOPHASE II
Chromosomes move to opposite poles
A nuclear envelope and membrane begins to re-form.
Cytoplasm begins to separate
Haploid

19. Remember PMAT
P= Pairs
M= Middle
A= Apart
T= Two