CELL DIVISION mitosis & meiosis
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Transcript of CELL DIVISION mitosis & meiosis
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I. Forms of DNAA. When the cell is NOT
dividing = chromatinB. When the cell IS dividing
= chromosome
Bivalentchromosome
Monovalentchromosome
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II. Why do cells divide?A. Replacement - cells wear
out & dieB. Repair - tissues can be
damaged by injury or infection
C. Growth of the organismD.Reproduction
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III.Types of cell divisionA. Mitosis
1. New cells are identical to the old cells
2. Chromosome number is the same in parent & daughter cells (diploid -2n)
3. Growth, repair, & asexual reproduction
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MITOSIS
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B.Meiosis1.Parent cell divides twice
to produce 4 cells2.Produces gametes (sex
cells –sperm/eggs)3.Daughter cells have half
the original number of chromosomes (haploid -1n)
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4.When two gametes join to form a zygote, it will have the normal # of chromosomes
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MEIOSIS
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5. Daughter cells are not Genetically identical a.) Homologous
chromosomes separate, sending one version of each to the new cells.
b.) Crossing –Over: sometimes chromosomal segements are exchanged between Homologous Chromosomes.
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IV.Phases of MitosisA. Interphase
1. Growth & normal cell activities
2. DNA = chromatin
*as the cell prepares for division, DNA is duplicated
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B.Prophase1.Chromatin thickens
& reveals duplicated chromosomes (bivalent)
2.Centrioles move to poles
3.Nuclear membrane dissolves
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C.Metaphase1.Bivalent
chromosomes line up along equator of cell
2.Chromosomes attach to spindle fibers
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D.Anaphase1.Spindle fibers pull monovalent chromosomes to opposite ends of cell
**an identical set of chromosomes moves to each pole
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E.Telophase1.Chromosomes
uncoil & become chromatin again – Nuc. Memb Reforms
2.Cytokinesis: cell membrane pinches in to form 2 separate cells
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V. Phases of MeiosisI. Cells go through two
rounds of division during meiosis, resulting in 4 haploid cells
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Meiosis I & IISection 11-4
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