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Cell Cycle: Meiosis Module 11
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Cell Cycle: Meiosis Module 11

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Questions and Answers

What is the primary purpose of meiosis?

  • To double the chromosome number in a cell
  • To create four genetically diverse haploid cells (correct)
  • To repair damaged cells
  • To create two identical diploid cells
  • During which phase of meiosis II do the sister chromatids separate?

  • Anaphase II (correct)
  • Metaphase II
  • Prophase II
  • Telophase II
  • What are homologous chromosomes?

  • Identical chromosomes from the same parent
  • Chromosomes that carry the same genes but may have different alleles (correct)
  • Chromosomes that are identical in every way
  • Chromosomes that are not related in any way
  • What results from cytokinesis in meiosis II?

    <p>Four genetically distinct haploid cells are produced</p> Signup and view all the answers

    Which of the following best describes non-disjunction?

    <p>The failure of chromosomes or chromatids to separate properly</p> Signup and view all the answers

    What is crossing-over during meiosis?

    <p>The exchange of genetic material between homologous chromosomes</p> Signup and view all the answers

    What occurs during prophase II of meiosis II?

    <p>Chromosomes condense and spindle apparatus forms</p> Signup and view all the answers

    What structure reforms around separated chromosomes during telophase II?

    <p>Nuclear envelope</p> Signup and view all the answers

    What is the primary purpose of meiosis in sexually reproducing organisms?

    <p>To reduce the chromosome number by half</p> Signup and view all the answers

    During which phase of Meiosis I do homologous chromosomes form bivalents?

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

    What occurs during crossing-over in Meiosis I?

    <p>Homologous chromosomes exchange segments</p> Signup and view all the answers

    Which statement describes the outcome of Telophase I in meiosis?

    <p>Two haploid daughter cells are produced</p> Signup and view all the answers

    What is the significance of reducing the chromosome number during meiosis?

    <p>To maintain the chromosome number across generations</p> Signup and view all the answers

    In which phase do the spindle fibers attach to homologous chromosomes?

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

    What happens to the homologous chromosomes during Anaphase I?

    <p>They separate and move to opposite poles</p> Signup and view all the answers

    Which phase of meiosis is primarily responsible for ensuring genetic variability?

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

    What is the primary purpose of meiosis?

    <p>To reduce chromosome numbers and create genetic diversity</p> Signup and view all the answers

    How many daughter cells are produced at the end of meiosis?

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

    What occurs during Prophase I of meiosis that increases genetic variation?

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

    Which of the following statements is true about mitosis compared to meiosis?

    <p>Mitosis results in genetically identical daughter cells</p> Signup and view all the answers

    What chromosome abnormality is associated with Down syndrome?

    <p>Extra copy of chromosome 21</p> Signup and view all the answers

    What type of errors in meiosis can lead to genetic disorders?

    <p>Nondisjunction and translocation</p> Signup and view all the answers

    During which phase of meiosis are sister chromatids separated?

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

    Which of the following statements is true for both meiosis and mitosis?

    <p>Both involve DNA replication</p> Signup and view all the answers

    Study Notes

    Overview of Meiosis

    • Meiosis reduces chromosome number by half, from diploid (2n = 46) to haploid (n = 23).
    • Occurs solely in reproductive cells of sexually reproducing organisms.
    • Key function: ensures genetic variability and maintains chromosome number across generations.

    Phases of Meiosis

    Meiosis I: Reductional Division

    • Reduces chromosome number from diploid to haploid.
    Phases of Meiosis I
    • Prophase I:

      • Chromosomes coil and become visible (Leptonema).
      • Homologous chromosomes pair (Zygonema), forming bivalents (two homologous chromosomes).
      • Crossing-over occurs (Pachynema), ensuring genetic diversity.
      • Homologous chromosomes begin to separate; chiasmata become visible (Diplonema).
      • Chromosomes fully condense; chiasmata move to ends; nuclear envelope breaks down (Diakinesis).
    • Metaphase I:

      • Homologous chromosomes align on the metaphase plate.
      • Spindle fibers attach from opposite poles to chromosomes.
    • Anaphase I:

      • Homologous chromosomes separate and move to opposite poles.
      • Sister chromatids remain attached at the centromere.
    • Telophase I:

      • Homologous chromosomes complete migration to poles.
      • Nuclear envelope reforms; cytokinesis creates two haploid daughter cells.

    Meiosis II: Equational Division

    • Similar to mitosis, separates sister chromatids while maintaining haploid number.
    Phases of Meiosis II
    • Prophase II:

      • Spindle apparatus reforms; chromosomes condense in preparation for division.
    • Metaphase II:

      • Chromosomes align on the metaphase plate; kinetochores face opposite poles.
    • Anaphase II:

      • Centromeres split; sister chromatids move to opposite poles as individual chromosomes.
    • Telophase II:

      • Nuclear envelopes reform around separated chromosomes.
      • Cytokinesis occurs, resulting in four non-identical haploid daughter cells.

    Key Terms

    • Meiosis: Cell division producing four genetically diverse haploid cells from one diploid parent cell.
    • Diploid (2n): Cells with two complete chromosome sets (46 in humans).
    • Haploid (n): Cells with one complete chromosome set (23 in humans).
    • Homologous Chromosomes: Chromosome pairs from each parent, similar in structure and genetic content.
    • Synapsis: Pairing of homologous chromosomes.
    • Bivalent/Tetrad: Homologous chromosome pair consisting of four chromatids.
    • Crossing-over: Exchange of genetic material between homologous chromosomes.
    • Chiasma: Points at which homologous non-sister chromatids cross over.
    • Nondisjunction: Failure of chromosome separation leading to genetic disorders.
    • Cytokinesis: Division of the cytoplasm, resulting in distinct cells.

    Key Points to Remember

    • Purpose of meiosis: reduce chromosome number and create genetic diversity via recombination.
    • Differences between Meiosis I & II:
      • Meiosis I reduces chromosome number; Meiosis II separates sister chromatids.
    • Errors in meiosis (nondisjunction, translocation, deletion) can lead to significant genetic disorders.
    • Crossing-over during Prophase I is vital for genetic variation in offspring, crucial for sexual reproduction.

    Comparison: Mitosis vs. Meiosis

    • Number of Cell Divisions: Mitosis (1), Meiosis (2).
    • Number of Daughter Cells: Mitosis (2), Meiosis (4).
    • Genetic Identity: Mitosis (identical to parent), Meiosis (genetically different from parent).
    • Chromosome Number: Mitosis (diploid, 46), Meiosis (haploid, 23).
    • Location of Occurrence: Mitosis (somatic cells), Meiosis (gametes).
    • Timing: Mitosis (throughout life); Meiosis (during sexual maturity).
    • Primary Role: Mitosis (growth, repair); Meiosis (sexual reproduction, genetic diversity).

    Common Errors in Meiosis

    • Nondisjunction: Leads to genetic disorders such as:
      • Down Syndrome: Extra copy of chromosome 21.
      • Klinefelter Syndrome: Additional X chromosome (XXY).
      • Turner Syndrome: Missing X chromosome in females (XO).

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    Description

    Test your understanding of the different phases of meiosis with this quiz. Learn about the key events that occur during meiotic cell division, which reduces the chromosome number from diploid to haploid, specifically in reproductive cells. Perfect for reinforcing concepts covered in Module 11.

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