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UNIT 9 OBJECTIVES - MITOSIS AND MEIOSIS Dates: Dec. 4 – Dec. 12 Chapters: 5 Assignments: Investigation 22 - Mitosis Investigation 23 Limits of Cell Growth Cancer Handouts Handout - Mitosis and Meiosis worksheets Investigation 24 Case of the Dividing Cell Evaluation: Dec. 12th - TEST - DNA-RNA (Unit 8) and Mitosis and Meiosis Introduction: DNA has been found to be the genetic code, the blueprint for all cellular activity. As we now know, it is located on the chromosomes in the nucleus of eukaryotic cells. The chromosome number may vary from organism to organism but one characteristic of each organism is that each of their body (somatic) cells always maintains the same number of chromosomes. The Cell Theory states that cells come from other cells; meaning that cells divide to produce two new cells called daughter cells. These are identical to the parent cell in respect to the number of chromosomes they have and the blueprint they carry. The ability of DNA to duplicate itself gives the nucleus the ability to copy itself. This is called mitosis. The division of the cytoplasm (Cytokinesis) follows this by dividing the cell in half. For some organisms, this may be a form of reproduction called Asexual; for multicellular organisms, it is a way to increase the number of cells thus increasing the size of the organism, or helping to repair or replace old or dying cells. Meiosis is another form of cell division that is a necessary process for those organisms that carry out sexual reproduction. In sexual reproduction, there is a combination of chromosomes to make the offspring. Half come from the female and half from the male. The specialized cells that join are called gametes or sex cells (better known as egg and sperm). To maintain the proper number of chromosomes for the species, these cells must undergo a different kind of cell division than mitosis. This process is called meiosis and is a reduction division or a reduction of the chromosome number by one-half to form gametes. This process does not take place just anywhere in the body, it occurs only in the gonads (ovaries and testes) that produce the sex cells. At the conclusion of this unit the student should be able to: 1. explain why cells divide and under what cellular conditions might they be stimulated to divide. a. What happens to the surface-to-volume ratio of a cell as it grows? 2. explain the purpose of mitosis. Cytokinesis. 3. list and describe the phases of the cell cycle. 4. explain the importance of metaphase. 5. distinguish between cell division in an animal cell and cell division in a plant cell. 6. define Meiosis I and Meiosis II. 7. explain the importance of Meiosis to sexually reproducing organisms. chromosomal characteristics of that species? How does it continue the 8. using cell division in your explanation, define cancer. Explain why it is such a dangerous disease. Vocabulary: somatic cells cancer cytokinesis mitosis meiosis chromosome chromatid centromere chromatid centromere centrioles spindle fibers tetrad haploid (monoploid) (1n) homologous crossing-over synapsis mutation diploid (2n) Extra Credit: 1. A cell is 3um long, 3um wide, and 3 um high. Find the ratio of volume to surface area. 2. Using reference sources, investigate the relationship between mitosis and cancer. What phases of mitosis might you expect to observe most frequently?