1. 9.5 Meiosis in Sexual Reproduction

2. Gametes = Haploid Sex Cells (sperm/egg)
Haploid cells have only one set of chromosomes, abbreviated as “n”
Diploid cells are those with two (di) sets = “2n”
Gametes = Haploid Sex Cells (sperm/egg)

3. Already duplicated in preparation for division
Homologous chromosomes:   A pair of chromosomes in which one member of the pair is obtained from the organism's maternal parent and the other from the paternal parent; found in diploid cells.
Already duplicated in preparation for division

4. Humans _____Chromosomes, ______Pairs
One from Mom One from Dad
2 Gametes (n) join during fertilization forming a 2n cell called a Zygote.

5. Mitosis starts with 1 2n cell ends with 2 2n cells genetically identical
Meiosis starts with 1 2n cell ends with 4 n cells genetically mixed

6. Two divisions occur, Meiosis I (Reduction) and Meiosis II (Division)
Prophase I Unique Event!!! Homologues group forming tetrads - Crossing over occurs - chromatids break and may be reattached to a different homologous chromosome

8. Metaphase I - tetrads line-up along the equator of the spindle
Metaphase I - tetrads line-up along the equator of the spindle. Spindle fibers attach to the centromere region of each homologous chromosome pair
Anaphase I - tetrads separate, and are drawn to opposite poles by the spindle fibers. The centromeres in Anaphase I remain intact.

9. Telophase 1 & Cytokinesis occurs
NO INTERPHASE AKA NO DNA REPLCIATION
PMAT STARTS ALL OVER AGAIN
Prophase II  Metaphase II  Anaphase II  Telophase II
Occur similar to mitosis.

14. Or 8,400,000 possible gamete combinations!
Possible gamete combinations = 2n where n is the number of chromosomes
So humans its 223
Or 8,400,000 possible gamete combinations!