Mitosis & Meiosis

1. Mitosis & Meiosis Coleman Honors Biology 2008-2009

2. Surface Area: Volume Surface Area: amount of cell membrane available to transport nutrients and waste. Volume: the amount of space the internal cell parts take up. As a cell grows, it’s volume increases faster than its surface areacausing two big problems… Too many demands on DNA 2. No enough surface area to get nutrients in and waste out efficiently

4. Cell Parts • Cell Membrane: protects internal contents of cell; controls flow of materials into and out of cell. • Nucleus: control center of cell; contains DNA • Nuclear membrane: protects internal contents of nucleus; contains pores which allow information to move in and out of cell • Nucleolus: site for ribosome production • Chromatin: strands of DNA wound around proteins • Chromosomes: packages of DNA; can only be seen during cell division; 23 from Mom & 23 from Dad. • DNA: molecule which holds genetic information • Centriole: cell part found in cytoplasm, will help organize cell parts during cell division • Spindle: microtubules which extend from centriole; will control chromosomes during cell division

6. Cell Cycle: Overview • Interphase • G1 Phase: cell grows • S-phase: DNA & organelles replicate • G2 Phase: cell grows • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis

7. The Cell Cycle Section 10-2 G1 phase M phase S phase G2 phase Go to Section:

8. Drawing Mitosis

9. Meiosis: The creation of gametes (sex cells) which have half the number of chromosomes than a normal body cell and are all genetically different; created so that sexual reproduction can occur. Diploid Cell: regular body cell; contains two complete sets of chromosomes (1 set from mom/1 set from dad) Diploid Number: number of chromosomes (human dipoid # is 46)

10. Haploid Cell: Cell which contains half the number of chromosomes as a normal body cell Haploid Number: number of chromosomes in a haploid cell (human haploid # is 23) Homologous Chromosomes: two chromosomes that carry information about the same traits (1 from mom/1 from dad) Crossing Over: when homologous chromosomes exchange genetic information. Tetrad: Paired homologous chromosomes (4 chromatids total)

11. Crossing-Over Crossing over of tetrad. Occurs during Prophase I of Meiosis. Necessary for genetic diversity of reproductive cells (gametes). Section 11-4 Go to Section:

12. Figure 11-15 Meiosis Section 11-4 Meiosis I 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. Go to Section:

13. Figure 11-17 Meiosis II Section 11-4 Meiosis 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. Go to Section: