1. Sexual Reproduction
Meiosis

2. Sexual Reproduction Our body cells all have 46 chromosomes
DIPLOID: Two copies of each chromosome - 23 from our mom, 23 from our dad
HOMOLOGOUS CHROMOSOME: chromosomes that have the same type of information on them
Same length and shape
All diploid cells have homologous chromosomes
Exception: sex cells (eggs and sperm) have half the number of chromosomes as other body cells
HAPLOID: one copy of each chromosome
MEIOSIS: type of cell division that halves the chromosome number to make sperm and eggs
Cells go from diploid to haploid
Make 4 cells from one cell

3. MEIOSIS
Follows the same basic steps as mitosis with one critical difference
Steps of both types of cell division:
Prophase: nuclear membrane breaking down, centrioles are beginning to form spindle fibers
Metaphase: chromosomes line up along equator, spindle fibers attached to chromosomes
Anaphase: chromosomes split in half, separate to the poles being pulled by spindle fibers
Telophase: chromosomes at poles, nuclear membrane reforms

4. Meiosis follows the same basic steps of mitosis but begin with tetrads
TETRAD: homologous chromosomes come together and move as a unit
While homologous chromosomes are side by side, similar pieces of chromosomes can swap, switching genetic material CROSSING OVER
Meiosis I: chromosomes form tetrads in prophase
Metaphase: Line tetrads up at equator
Anaphase: Divide tetrads in half
Telophase: first division ends up with two cells that have double stranded chromosomes
Meiosis II: divide each cell again to form single stranded chromosomes in each cell - exact same steps as mitosis

5. COPY DIAGRAM

6. Crossing Over

7. DRAW IN NOTES
Homologous
Not Homologous

8.  + +  Tetrad COPY INTO NOTES Homologous Chromosome Homologous

17. Assignment
Worksheet: Comparing Meiosis and Mitosis
Due next day