Cell Division: Mitosis Overview
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Questions and Answers

What occurs during the Gap 2 phase of the cell cycle?

  • DNA replication occurs.
  • Chromosomes condense into chromatin.
  • The cell grows and produces new proteins. (correct)
  • Cytokinesis takes place.

    • What marks the end of prophase in mitosis?

  • Chromatin condensing into visible chromosomes. (correct)
  • The separation of chromatids.
  • Spindle fibers aligning the chromosomes.
  • The formation of the nuclear membrane.

    • Which statement about anaphase is accurate?

  • The nucleolus reappears.
  • Chromosomes are pulled towards opposite ends of the cell. (correct)
  • Centrioles move towards the nucleus.
  • Chromatids align along the metaphase plate.

    • What distinguishes cytokinesis in animal cells from that in plant cells?

    <p>A fiber ring composed of actin contracts in animal cells.</p> Signup and view all the answers

    During which phase do chromosomes become attached to spindle fibers?

    <p>Metaphase</p> Signup and view all the answers

    What occurs during anaphase I of meiosis?

    <p>Homologous chromosomes separate and move to opposite poles while sister chromatids remain attached.</p> Signup and view all the answers

    What distinguishes metaphase II from metaphase I in meiosis?

    <p>Single chromosomes align on the metaphase plate.</p> Signup and view all the answers

    What is the result of cytokinesis following telophase I in meiosis?

    <p>Two haploid cells are formed with replicated chromosomes.</p> Signup and view all the answers

    What happens to the chromosomes after telophase I in rapid meiosis?

    <p>Chromosomes remain condensed without decondensing.</p> Signup and view all the answers

    Which statement about prophase II is correct?

    <p>There is no replication of chromosomes before meiosis II.</p> Signup and view all the answers

    Study Notes

    Cell Division Overview

    • Two main types of cell division: mitosis and meiosis
    • Mitosis: division of somatic (body) cells
    • Meiosis: division of gametes (sex cells)

    Mitosis

    • Mitosis is nuclear division plus cytokinesis
    • Results in two identical daughter cells
    • Stages include prophase, prometaphase, metaphase, anaphase, and telophase
    • Interphase is not part of mitosis, but encompasses G1, S, and G2 of the cell cycle

    Phases of Mitosis

    • Interphase: Cell grows, replicates its chromosomes, and prepares for division
      • Contains G1 (cell growth), S (DNA synthesis), and G2 (cell growth) phases
      • Chromosomes are not clearly visible
      • Nucleolus is visible
      • Centrioles (or microtubule organizing centers in plants) are present.
    • Prophase: Chromatin condenses, becomes visible chromosomes. Nucleolus disappears
      • Chromosomes thicken, shorten and become paired.
      • Two chromatids joined by a centromere
      • Centrioles move to opposite ends of cells and fibers extend from centromeres
      • Some fibers form the mitotic spindle.
    • Metaphase: Spindle fibers align chromosomes along middle of cell nucleus (metaphase plate)
      • Chromosomes are thick and coiled
      • Spindle fibers connect to chromosomes via centromeres
      • Homologous chromosomes do not associate
    • Anaphase: Paired chromosomes separate at kinetochores and move to opposite sides of the cell
      • Spindle fibers separate sister chromatids
      • Chromosome movement results from a combination of interactions.
    • Telophase: Chromatids arrive at opposite poles
      • New membranes form around nuclei
      • Chromosomes disperse and are no longer visible in light microscope
      • Spindle fibers disperse
      • Cytokinesis may begin

    Cytokinesis

    • Process of dividing the cytoplasm
    • In animal cells: actin fiber ring contracts, pinching cell into two
    • In plant cells: cell plate synthesized between two daughter cells

    Meiosis

    • Produces haploid gametes
    • Reduces chromosome number by half
    • Occurs only in special cells
    • Results in four haploid daughter cells
    • Consists of Meiosis I and Meiosis II (each with similar stages to mitosis phases such as Prophase I, Metaphase I, and Telophase I, also Prophase II, Metaphase II, and Telophase II).

    Meiosis I

    • Prophase I: Duplicated chromosomes pair, cross over, and become visible
    • Metaphase I: Paired homologous chromosomes align on a plane equidistant from the poles (metaphase plate)
    • Anaphase I: Homologous chromosomes separate and move to opposite poles (sister chromatids remain attached)
    • Telophase I: Homologous chromosome pairs complete migration, forming two haploid sets at opposite poles, followed by cytokinesis

    Meiosis II

    • Interphase (before Meiosis II): No chromosome replication takes place
    • Prophase II: Spindle forms; the nuclear envelope breaks down
    • Metaphase II: Chromosomes align on the metaphase plate
    • Anaphase II: Sister chromatids separate, becoming chromosomes
    • Telophase II: Chromosomes complete migration and cytokinesis results in forming four haploid daughter cells

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    Cell Division: Mitosis and Meiosis (OCR)

    Description

    Explore the fascinating processes of cell division with a focus on mitosis. This quiz covers key stages, including interphase, prophase, and the overall significance of mitosis in somatic cell division. Test your understanding of how cells replicate and prepare for division.

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