1. Meiosis & Fertilization
State Standard LS1I

2. Things to Remember 1. Asexual Reproduction
All living things REPRODUCE
two types of reproducing:
1. Asexual Reproduction
Produces cells that are IDENTICAL copies of parent cell
2. Sexual Reproduction
Combines genetic material of 2 parents so offspring are genetically DIFFERENT from parents

3. Sexually Reproducing Males
SPERMATOGENESIS = MAKING MATURE SPERM
Process occurs in the TESTES
Begins with Primary SPERMATOCYTES
Process of meiosis yields 4 SPERM (gametes)
The process occurs constantly throughout life

4. Sexually Reproducing Females
OOGENESIS = MAKING a Mature Egg
Process occurs in the Ovaries
Begins with Primary OOCYTES
Process of meiosis yields 1 Egg (gametes), and 3 polar bodies
Cytoplasm divides unevenly
Polar bodies degenerate
Females are born with a finite number of Eggs.

5. Interphase I
Cells undergo a round of DNA replication, forming duplicate chromosomes

6. Prophase I
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.

7. Metaphase I
Spindle fibers attach to the chromosomes

8. Anaphase I
The fibers pull the homologous chromosomes toward opposite ends of the cell.

9. Telophase I and Cytokinesis
Nuclear membranes form. The cell separates into two cells.

10. Analysis Questions
Describe in your own words the events of this first meiotic division.
What other chromosomal patterns might have resulted in the daughter cells? (you may wish to move your model pieces around to help illustrate the possibilities.
How many chromosomes does each daughter cell now have? What helped you determine that number?

11. Prophase II
DNA condenses into chromosomes and spindle fibers are formed.

12. Metaphase II
The chromosomes line up in a similar way to the metaphase stage of mitosis.

13. Anaphase II
The sister chromatids separate and move toward opposite ends of the cell.

14. Telophase II
Cells begin to divide, forming daughter cells.

15. Analysis Questions
Describe in your own words what has taken place in Meiosis II. Indicate which chromosome came from which parent in each of the resulting cells.
What is the difference between the starting cell (primary spermatocyte or oocyte) and the cells at the end of Meiosis I? Between the cells at the end of Meiosis I and the cells at the end of Meiosis II?
Describe why you think meiosis is a significant process in terms of: The passing on of information from generation to generation
Variation of traits among siblings

16. Meiosis
Meiosis is the way to make cells with ½ the number of chromosomes for sexual reproduction
Meiosis Crash Course