Biology: Mitosis Stages
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Questions and Answers

What is the phase called when a cell is not dividing?

  • Interphase (correct)
  • G1-phase
  • Meiosis
  • Mitosis

    • What is the typical duration of the M-phase of the cell cycle?

  • 1-2 months
  • 1-2 hours (correct)
  • 1-2 weeks
  • 1-2 days

    • What happens to the G1 and G2 phases during cleavage of zygote and blastomeres in mammalian development?

  • They remain unchanged
  • They are abolished (correct)
  • They are prolonged
  • They are shortened

    • What is the special G1 state called when cells have completely ceased cycling?

    <p>G0-phase</p> Signup and view all the answers

    What is the term for the alternation between mitosis and interphase in the life of a cell?

    <p>Cell division cycle</p> Signup and view all the answers

    What is the longest phase of the cell cycle?

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

    What type of cells have a very short or non-existent G1 phase?

    <p>Rapidly dividing cells</p> Signup and view all the answers

    How long can the G1 phase last in hepatocytes?

    <p>One-half to one year</p> Signup and view all the answers

    During which stage of mitosis does the nuclear envelope and nucleolus disappear?

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

    What happens to the sister chromatids during early anaphase?

    <p>They move towards the opposite poles of the cell</p> Signup and view all the answers

    What happens to the microtubules during late anaphase?

    <p>They lengthen and pull the sister chromatids apart</p> Signup and view all the answers

    During which stage of mitosis do the poles move farther apart?

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

    What appears in the equatorial plane of the cell membrane during late anaphase?

    <p>A cleavage furrow</p> Signup and view all the answers

    What happens to the chromosomes during meiosis?

    <p>They are duplicated during the S phase</p> Signup and view all the answers

    When does telophase begin?

    <p>After the chromosomal movement stops</p> Signup and view all the answers

    What happens to the nucleolus during prophase?

    <p>It disappears</p> Signup and view all the answers

    What is the result of the fusion of two haploid cells?

    <p>A diploid zygote or diploid cell</p> Signup and view all the answers

    What is the point of attachment of the spindle microtubules to the chromosome?

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

    What is the symbol for the number of chromosomes in a diploid cell?

    <p>2n</p> Signup and view all the answers

    What happens during cytokinesis?

    <p>The cleavage furrow deepens and divides the cytoplasm and organelles in half</p> Signup and view all the answers

    What is the term for the process of non-sister chromatids exchanging bits during prophase I?

    <p>Crossing over</p> Signup and view all the answers

    What is the longest part of meiosis?

    <p>Prophase I</p> Signup and view all the answers

    What is the number of cells that result from meiosis?

    <p>4 cells</p> Signup and view all the answers

    What is the term for half the diploid number of chromosomes?

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

    What are the two broad events that cell division consists of?

    <p>Nuclear division or karyokinesis, and cytoplasmic division or cytokinesis</p> Signup and view all the answers

    What happens to the DNA during the S-phase of the cell cycle?

    <p>It is doubled from 2N to 4N</p> Signup and view all the answers

    What is the result of DNA replication during the S-phase?

    <p>Each chromosome becomes a pair of sister chromatids</p> Signup and view all the answers

    What happens to the nuclear envelope during prophase?

    <p>It remains intact</p> Signup and view all the answers

    What happens to the centrioles during prophase?

    <p>They separate and migrate to opposite poles of the cell</p> Signup and view all the answers

    What is the result of the spindle microtubules during prophase?

    <p>They appear between the centrioles</p> Signup and view all the answers

    What is the characteristic of the chromosomes during Prophase II?

    <p>The sister chromatids are still coupled together at the centromere</p> Signup and view all the answers

    What happens to the chromosomes during Metaphase II?

    <p>The chromosomes move to the equatorial plane</p> Signup and view all the answers

    What is the result of Anaphase II?

    <p>The centromeres separate and the sister chromatids are pulled apart</p> Signup and view all the answers

    What is the final result of Telophase II?

    <p>The former sister chromatids have reached the poles and a nuclear envelop is formed around each nucleus</p> Signup and view all the answers

    What is the role of Meiosis in sexually reproducing eukaryotes?

    <p>It preserves the genome size and provides mechanisms to diversify the genomes of the offspring</p> Signup and view all the answers

    What is the orientation of the equatorial plane during Metaphase II with respect to the previous one of meiosis I?

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

    What happens to the sister kinetochores during Meiosis?

    <p>They pull both sister chromatids toward one pole of the cell</p> Signup and view all the answers

    What is the stage of Meiosis where the chromosomes condense again?

    <p>Prophase II</p> Signup and view all the answers

    Study Notes

    Mitosis

    • Mitosis is a process of cell division characterized by four stages: Prophase, Metaphase, Anaphase, and Telophase.
    • In Prophase, the nucleolus disappears, and the nuclear membrane breaks down.
    • In Metaphase, the nuclear envelope and nucleolus disappear, and the chromosomes occupy the equatorial plane of the spindle microtubules.
    • In Anaphase, sister chromatids migrate towards the opposite poles of the cell, following the direction of the spindle microtubules.
    • In Telophase, the reappearance of the nuclei in daughter cells occurs, and the chromosomes revert to their semi-dispersed state.

    Cytokinesis

    • Cytokinesis is the process of cell division, characterized by the cleavage furrow progressing until it divides the cytoplasm and its organelles in half.

    Meiosis

    • Meiosis is a process of cell division characterized by two consecutive divisions: Meiosis I and Meiosis II.
    • No DNA synthesis (or S phase) occurs between the two divisions.
    • Four cells result, each with half the number of chromosomes of the starting cell (2n → n).
    • Fusion of two such cells produces a 2n zygote or diploid zygote.

    Symbols and Terminologies

    • Diploid: a set of 23 pairs of chromosomes (or 46) symbolized as 2n.
    • Haploid: half the diploid number of chromosomes (or 23) symbolized as n.
    • DNA in a diploid cell before S-phase is 2N.
    • After the S-phase (duplication of DNA) in preparation for mitosis, the DNA is 4N.

    Meiosis I

    • In Prophase I, the chromosomes become visible, already doubled, with each homologue having been duplicated during the preceding S phase.
    • Non-sister chromatids exchange bits, a process called crossing over or chiasmata formation.
    • It is the longest part of meiosis.

    Meiosis II

    • In Metaphase II, microtubules of the spindle fibers attach to sister kinetochores of one homologue, pulling both sister chromatids toward one pole of the cell.
    • In Anaphase II, the centromeres separate, and the sister chromatids are pulled apart to opposite poles by the spindle.
    • In Telophase II, the former sister chromatids reach the poles, and a nuclear envelope is formed around each nucleus, while chromosomes uncoil again.

    Genetic Recombination

    • Meiosis not only preserves the genome size of sexually reproducing eukaryotes but also provides three mechanisms to diversify the genomes of the offspring.

    Cell Division Cycle

    • Every living cell that is not dividing exists in a phase called Interphase.
    • Interphase lasts for a variable duration from a few hours to a year or more.
    • When a cell is dividing, it enters a phase called Mitosis.
    • The alternation between mitosis and interphase in the life of a cell is called the cell division cycle.

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    Quiz on the stages of mitosis, including prophase and metaphase, covering the breakdown of the nuclear membrane and the movement of chromosomes.

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