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Chapter 10 Cell Division

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Chapter 10 Cell Division

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    1. Chapter 10 Cell Division L2 Biology

    2. Size of most eukaryotic cells: 10-100 micrometers (um) Diameter of high power field of view in our scopes is 500 um (0.5 mm)

    3. A crocodile and an earthworm have cells the same size.Why is that?

    4. Read pp 242-243 in your textbook. Surface area to volume ratio determines how long cells can grow before they either die or divide: As cells grow larger, their surface area to volume ratio (increases or decreases?). If the volume is so big that stuff cant diffuse into or out of the entire cell in a reasonable amount of time, the cell will die from waste buildup or starvation.

    5. If these were cells, which would be most efficient in taking in and getting rid of materials in the same amount of time?

    6. Why do cells divide? Growth

    7. Cells go through a life cycle

    8. Cell cycle phases: These only occur if a cell is going to divide G1 = cell grows after being formed S DNA makes a copy of itself in preparation for cell division G2 short growth phase M mitosis nucleus is copied If a cell is not going to divide, it stays in G0 phase doesnt prepare for cell division.

    10. Chromatin Invisible most of the time - Only visible during cell division (mitosis or meiosis) During S-phase the DNA replicates (makes an exact copy of itself) This means the cell has twice as much DNA in it after replication Once a chromosome has replicated, it shortens and thickens and can now be seen in our microscopes.

    11. One Chromosome Sister Chromatids Each strand is an identical copy of the other one Centromere Where the two chromatids Are attached to each other This is different for each chromosome

    12. Chromosome Number Each species has the same number of chromosomes in all their cells that are made by mitosis. This is the diploid number (2n). In humans this number is 46. So cells of your skin and muscle and liver each have 46 chromosomes in them. Look how many chromosomes are in the cells of these creatures:

    13. These 46 chromosomes are actually pairs, one came from your father, one from your mother. So each of your cells has 23 pairs of chromosomes. Each member of the pair is homologous to the other of that pair (same length, centromere in same place, genes for same traits in same location).

    14. When cells divide by mitosis, each daughter cell receives the same number of chromosomes as its mother cell has 2n. In order to do this, the chromosomes must be copied first, then one of each copy is placed in the new cells.

    15. 22 Homologous pairs of chromosomes; one pair of sex chromosomes

    16. Sex Chromosomes Homologous in females: XX Not homologous in males: XY

    17. Mitosis Nuclear division resulting in nuclei identical to parent cell asexual reproduction for some organisms. Begins after interphase Ends before cytokinesis Four phases: Prophase Metaphase Anaphase Telophase

    18. Prophase

    20. Prophase Chromosomes become visible Spindle forms from protein microtubules Nuclear envelope disintegrates Nucleolus disintegrates In animal cells, centrioles migrate to opposite ends of the cell (poles) and spindle fibers attach to them

    21. Metaphase Chromosomes line up single file at the equator of the cell

    22. Anaphase Sister chromatids are pulled apart toward opposite poles

    23. Telophase Nuclear membrane forms around each group of chromosomes Nucleolus reappears in each nucleus Spindle fibers disappear Chromosomes become invisible again as chromatin Cytokinesis begins in plant cell by formation of cell plate; cleavage furrow in animal cell completely separates the two nuclei into two different cells.

    29. Why is cell division important to understand? Cancer is uncontrolled cell division cells then spread to other parts of the body.

    30. Skin cancer cells

    31. Meiosis Cell division producing cells that have half the number of chromosomes of the mother cell Produces gametes eggs and sperm Occurs so that fertilization doesnt increase the number of chromosomes in each generation.

    32. Gametes = sex cells Eggs or sperm Have half the normal number of chromosomes = haploid (n) = 23 in humans Sexual reproduction needs these to combine DNA from two different parents, producing offspring that is different from each parent

    33. Meiosis = Reduction Division Two complete cell divisions First cell division separates homologous chromosomes (reduction of chromosome number) Second cell division separates sister chromatids (like mitosis) - Division Produces 4 haploid cells

    34. M E I O S I S II

    36. Gametogenesis Oogenesis Production of an egg One mother cell produces one egg cell and three polar bodies that die Spermatogenesis Production of sperm One mother cell produces 4 equally sized sperm cells

    39. Fertilization

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