Mitosis vs. Meiosis Objective 1

Chromosomes X shaped Contain our DNA Humans have 46 (23 pairs) Each normal cell needs all 46 Gametes (sex cells) need 23

Review What are the shape of chromosomes? How many chromosomes do humans have? How many chromosomes are in our sex cells?

Mitosis Mitosis is regular cell division 1 cell  2 identical cells 99% of all cells are normal cells 46 chromosomes (23 pairs) 1 cell  2 identical cells Mitosis has 4 phases (steps) Prophase Metaphase Anaphase Telophase

Review What types of cells use mitosis to divide? What are the phases of mitosis? How many chromosomes do each daughter cell have after mitosis (in humans)?

Meiosis Meiosis is sex cell (gamete) division 23 chromosomes only (no pairs) 1 cell  4 unique gametes (sperm/egg) Meiosis has 8 steps (phases) Prophase I 5. Prophase II Metaphase I 6. Metaphase II Anaphase I 7. Anaphase II Telophase I 8. Telophase II

Meiosis Part 1 Interphase I Prophase I Metaphase I Anaphase I Cells undergo a round of DNA replication, forming duplicate Chromosomes. Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. Spindle fibers attach to the chromosomes. The fibers pull the homologous chromosomes toward the opposite ends of the cell.

Meiosis Part II Prophase II Metaphase II Anaphase II Telophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells.

Visual Web Based Model http://www.pbs.org/wgbh/nova/baby/divi_flash.html

Review How many cells are made from meiosis? How many chromosomes do they have (in humans)? How many phases are in meiosis?

Diploid vs. Haploid Diploid cells: Haploid cells: Diploid uses mitosis Standard cells (99% of all cells) 2 sets of chromosomes (2N) How do diploid cells divide? Haploid cells: Gametes (sex cells) 1 set of chromosomes (1N or N) How do haploid cells divide? Diploid uses mitosis Haploid uses meiosis

Answer the following questions in your notes: How many phases are in mitosis? List them in order. How many phases are in meiosis? List them in order. What type of cells do mitosis? What type of cells do meiosis? Mitosis makes ___ _________ cells. Meiosis makes ___ _________ gametes. Mitosis makes (haploid/diploid) cells, while meiosis makes (haploid/diploid) cells.