1. Chapter 4.3: MEIOSIS
Life Science

2. Meiosis (my Oh sus)
Meiosis – a part of sexual reproduction in which cells divide to form sperm cells in a male and egg cells in a female.

3. MEIOSIS I and II
1. Meiosis I – cells divide to produce two duplicate cells of 46 chromosomes.
2. Meiosis II- cells produced in Meiosis I divide to produce four cells with half the number of chromosomes= 23 chromosomes (in humans)

4. Look at the Cells during Meiosis…

5. Number of Cells Produced
Mitosis
Meiosis
Type of Reproduction
Type of Cell Produced
Number of Cells Produced
Number of Chromosomes

6. Recap… Asexual Reproduction – organism produced from ????? parent cell
Like Bacteria!!!
Sexual Reproduction – organism produced from ????? parent cells
Organism inherits traits from BOTH parents
Like You!!!

7. Sexual Reproduction
Sexual Reproduction- when 2 sex cells, usually an egg and sperm, come together.
Each sex cell contributes half the chromosomes…
***Half From MOM & Half from DAD!

8.  NEW VOCAB 
Fertilization- is the joining of an egg and a sperm, from two different organisms.
a. A Cell that forms from fertilization is called a Zygote.

9. NOT A ZEBRAGOAT!

10. GAMETES Gametes = SEX CELLS = Reproductive Cells
1. Egg- formed in Female reproductive organs
2. Sperm- formed in Male reproductive organs

11. CHAPTER HOME
Image Gallery
BACK TO IMAGE GALLERY

12. Human Diploid Cell
Body cells are Diploid because they contain 23 pairs of chromosomes!

13. Human Haploid Cell Sex cells are a little different…
Sex Cells are Haploid because they contain 23 single chromosomes!

14. Meiosis

15. MEIOSIS FLIP BOOK

16. Meiosis I Interphase I- Prophase I-
Chromatin is doubling & spreading out
Centrioles are doubling
Nucleus is growing
Prophase I-
Chromosomes double and pair 2 by 2
Nucleus disappears
Spindle Fibers appear
Centrioles move to opposite sides

17. Meiosis I Metaphase I- Anaphase I-
Chromosomes line up in MIDDLE 2 by 2
Spindle fibers attach to centromeres
Anaphase I-
Chromosomes move to centrioles
1 whole chromosome moves one way- other moves other way

18. Meiosis I Telophase I- The cell cuts in half Spindle Fibers disappear
Nucleus Appears
2 cells are formed (46 chromosomes each)

19. Meiosis II The 2 new cells divide again Repeats the 4 stages
Total of 4 sex cells are created, each with half the number of chromosomes
Page 109

20. Meiosis II Intermission- Cell takes a break… Prophase II-
Spindle Fibers appear
Nucleus disappears
Centrioles double and move to opposite ends

21. Meiosis II Metaphase II- Anaphase II-
Chromosomes line up in middle of cell
Spindle fibers attach to centrioles and centromeres
Anaphase II-
Half of chromsomes (chromatids) move to opposite ends

22. Meiosis II Telophase II- Yay we are finished our flip book!!!
Nucleus appears
4 Total Cells – (23 chromatids in each one)
Each cell has ½ the number of the original
Yay we are finished our flip book!!!