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Biology - Mitosis






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    Biology - Mitosis Biology - Mitosis Presentation Transcript

    • Cell Growth and Division Chapter 10
    • Reasons for Reproduction
      • To keep from growing too large
        • Travel distance
        • Amount of proteins/DNA
    • Chromosomes
      • DNA in one cell, stretched out, is 2 meters
      • Prokaryotes: single, circular chromosome
      • Eukaryotes: multiple chromosomes in nucleus
    • Chromosome Structure
      • DNA winds around proteins called histones , like beads on a string
      • When cells divide, the DNA must pack itself even more tightly
    • Chromosome Structure
    • Chromosome Structure
    • Chromosome Structure
    • Chromatids
      • Each of two strands is a chromatid
      • Two pair strands are sister chromatids
      • Centromere is the region at which they are held together
    • Preparing For Cell Division
      • Copy of DNA is made
      • In prokaryotes, DNA is attached to the cell membrane as the cell pinches itself into two
    • Mitosis Section 10.2
    • Review of Cell Features
      • Cell Membrane
      • Cytoplasm
      • Nucleus
      • Nuclear Membrane
      • Chromosomes
    • Cell Life Cycle
      • Cell Growth
      • Synthesis (copying) of DNA
      • Preparation for Mitosis (division)
      • Mitosis
      • Non-mitosis stages are called interphase
    • Interphase
      • First gap phase (G 1 ), cell grows and builds organelles
      • Synthesis phase (S), cell copies DNA
      • Second gap phase (G 2 ), cell creates structures called microtubules for mitosis
    • Mitosis Stage 1: Prophase
      • Chromosomes condense
      • Nuclear membrane breaks down
      • Mictrotubules organize into a spindle
    • Mitosis Stage 2: Metaphase
      • Chromosomes fully condensed
      • Nuclear membrane gone
      • Chromosomes line up at center
      • Spindle fibers link opposite poles and chromosomes
    • Mitosis Stage 3: Anaphase
      • Spindle fibers shorten, pulling sister chromatids apart
      • Each side of the cell has a full set of chromosomes
    • Mitosis Stage 4: Telophase
      • Nuclear membrane re-forms in each new cell
      • Chromosomes un-coil
      • Spindle and fibers dissolve
      • Cytokinesis begins
    • Cytokinesis
      • Occurs after mitosis, but before interphase
      • Cell membrane grows toward the center of the cell, “pinching” it in two
      • New cells are half the size of original
    • In Plant Cells
      • Cell wall must form between new cells
      • Occurs as vesicles holding cell-wall material line up across center, making the cell plate
    • Chromosome Number
    • Organism Number of Chromosomes Adder’ tongue fern 1,262 Carrot 18 Cat 32 Chimpanzee 48 Earthworm 36 Fruit Fly 8 Horse 64 Lettuce 18 Sand dollar 52
    • Chromosome Number
      • Chromosomes always come in pairs called “homologous chromosomes”
      • Two forms of the same gene located on each of the pair
    • Chromosome Number
      • Karyotype is an arranged photograph of all chromosomes
      • Humans have 23 pairs
      • Non-sex chromosomes are called autosomes
    • Diploid vs. Haploid Cells
      • Cells with two sets of chromosomes (normal cells) are said to be diploid (2 n )
      • Cells with one set of chromosomes are haploid ( n )
      • What human cells must be haploid?
    • Haploid Cells
      • Sperm and egg cells are haploid ( n )
      • They create an organism with diploid cells when merged
    • Critical Thinking Questions
      • What would happen if sperm and egg cells were diploid instead of haploid?
      • Is there a correlation between complexity of an organism and chromosome number? Explain.
      • Use your notes to describe the structure of a chromosome. Give some reasons whey DNA must be condensed.
      • What would happen to a cell if mitosis occurred without cytokinesis? Draw a picture to explain this.
      • Contrast cell division in the following three organisms: bacteria, rose, chipmunk.
      • Draw a diploid cell with 3 pairs of chromosomes (in interphase). Now, draw the same cell in all four stages of mitosis.
    • Regulation
    • Signals
      • Cell growth/division depends on protein signals and environmental factors
      • Examples: deep wounds heal; bacteria fill Petri dish
    • Checkpoints
      • Mitosis will not start/continue unless conditions are correct
      • Are conditions favorable?
      • Are there mistakes in synthesized DNA?
      • Are chromosomes attached to fibers correctly?
    • Cancer
      • Uncontrolled, unregulated cell division
      • Damage to DNA results in a mass of defective cells called a tumor