1. MEIOSIS

2. MITOSIS MEIOSIS cell division
one parent cell becomes two identical daughter cells
occurs in somatic cells (regular cells)
used for growth and repair
cell division
one parent cell creates four unique cells, each with HALF the DNA
occurs in germ cells /gametes
used for sexual reproduction

3. MEIOSIS produces sperm cells and egg cells occurs in two stages
MEIOSIS I: separation of homologous chromosomes
MEIOSIS II: separation of sister chromatids

4. PROPHASE I (DNA has already been duplicated in S phase)
DNA condenses into chromosomes
Nuclear envelope dissolves
Centrioles appear at opposite ends of the cell; spindle fibers attach to centromeres
PROMETAPHASE: chromosomes move towards the center of the cell

5. METAPHASE I Chromosome PAIRS line up at the metaphasal plate
Tetrad: pairs of chromosomes
CROSSING OVER can occur between chromosome pairs

6. CROSSING OVER: when chromosome pairs exchange equal amounts of DNA where they intersect
CHIASMA: the point of intersection; where “crossing over” occurs
Leads to increased genetic diversity

7. ANAPHASE I Spindle fibers contract
Tetrads are broken apart into chromosomes
Half of the DNA moves to one end of the pole; the other half moves to the other end

8. TELOPHASE I
Two daughter cells are created – each with HALF of the organism’s DNA
Each new cell is unique
Cytokinesis: the separation of cytoplasms

9. PROPHASE II Prophase II begins immediately NO INTERPHASE
Nuclear envelope dissolves, centrioles appear, spindle fibers form
PROMETAPHSE: chromosomes move toward the center of the cell

10. METAPHASE II
Individual chromosomes(sister chromatids) line up at the metaphasal plate

11. ANAPHASE II
Sister chromatids separate and move to opposite ends of their cells
Because of crossing over, each chromatid has its own unique DNA

12. TELOPHASE II Nuclear envelopes form around the new chromatids
Each new cell has its own unique DNA and contains half of the organism’s DNA

17. EMBRYONIC DIFFERENTIATION
DUE TOMORROW