Meiosis II and DNA Functions
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Meiosis II and DNA Functions

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Questions and Answers

What process increases genetic variation during meiosis?

  • Nondisjunction
  • Cytokinesis
  • Cell Growth
  • Crossing Over (correct)

    • What is the result of nondisjunction during meiosis?

  • An abnormal number of chromosomes (correct)
  • Normal chromosome number
  • Improved cell division
  • Increased genetic variation

    • During which phase of meiosis does crossing over typically occur?

  • Telophase II
  • Anaphase II
  • Metaphase I
  • Prophase I (correct)

    • In males, meiosis results in the production of how many viable sperm cells?

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

    Which of the following is a characteristic feature of meiosis in females?

    <p>Unequal division of cytoplasm</p> Signup and view all the answers

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

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

    Which of the following best describes the outcome of meiosis?

    <p>One diploid cell produces four haploid cells</p> Signup and view all the answers

    Which phase ensures that each daughter cell receives a complete set of chromosomes after division?

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

    What is the primary purpose of cell division in organisms?

    <p>Repair and replacement of damaged cells</p> Signup and view all the answers

    Which option accurately describes a parent cell during cell division?

    <p>A cell that divides to produce daughter cells</p> Signup and view all the answers

    What occurs during crossing over in meiosis?

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

    In which phase does nondisjunction commonly occur during meiosis?

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

    What is a key difference between meiosis in males and females?

    <p>Meiosis in males occurs continuously, while in females it is periodic</p> Signup and view all the answers

    Which term describes cells that are capable of uniting with another to form a new individual?

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

    What is the primary outcome of meiosis II in terms of chromosome composition in gametes?

    <p>Each gamete has a haploid number of chromosomes with a single chromatid each.</p> Signup and view all the answers

    What is the result of crossing over during meiosis?

    <p>Increased genetic variation among daughter cells</p> Signup and view all the answers

    Which statement correctly describes the structure of eukaryotic chromosomes?

    <p>They are linear and tightly coiled around histones</p> Signup and view all the answers

    How do human males differ from females in terms of sex chromosome composition?

    <p>Males have one X and one Y chromosome.</p> Signup and view all the answers

    What is the consequence of nondisjunction during meiosis?

    <p>It leads to gametes with an abnormal number of chromosomes.</p> Signup and view all the answers

    Which phase of meiosis is primarily responsible for increasing genetic variation?

    <p>Metaphase I through independent assortment.</p> Signup and view all the answers

    During which process do crossing over and recombination primarily occur?

    <p>Meiosis I.</p> Signup and view all the answers

    What is the function of DNA helicase during DNA replication?

    <p>It separates the double-stranded DNA into single strands.</p> Signup and view all the answers

    What is the significance of telomeres in cellular processes?

    <p>They protect chromosomes from damage and are linked to aging.</p> Signup and view all the answers

    What serious condition is associated with extremely short telomeres at birth?

    <p>Hoyeraal-Hreidarsson Syndrome.</p> Signup and view all the answers

    Study Notes

    Meiosis II (Equational Division)

    • Haploid cells divide again, separating sister chromatids
    • Each gamete has a haploid number of chromosomes (n), with each chromosome now a single chromatid
    • Autosomes are numbered chromosomes (humans have 22 pairs)
    • Sex Chromosomes determine biological sex
      • Females have two X chromosomes (XX)
      • Males have one X and one Y chromosome (XY)

    DNA Helicase and DNA Polymerase

    • DNA Helicase acts as an "unzipper" to separate double-stranded DNA into single strands, creating a replication fork
    • DNA Polymerase adds nucleotides complementary to the template strand, essentially copying genetic information

    Telomeres

    • Telomere are protective caps of noncoding, repetitive DNA at the ends of chromosomes
    • Telomeres naturally shorten with each division
    • Short telomeres can contribute to cell death and overall aging
    • Some cells rebuild their telomeres:
      • Single-celled eukaryotes
      • Cells producing gametes
      • Embryos
    • Too much telomere rebuilding can lead to uncontrolled cell division (cancer)
    • Too little rebuilding can result in premature aging (Hoyeraal-Hreidarsson Syndrome)

    Hoyeraal-Hreidarsson Syndrome

    • Telomeres are too short at birth
    • Suffer premature organ and bone marrow failure
    • Life Expectancy is 2-3 years

    Cancer

    • Characterized by unrestrained cell growth and division, damaging adjacent tissues
    • It's the second leading cause of death in the United States
    • Occurs when DNA disruption interferes with cell division regulation

    Illustrations

    • Homologous chromosomes are the same size and shape, representing one chromosome from each parent
    • The centromere is the constricted area connecting two sister chromatids
    • Sister Chromatids are identical copies of a chromosome, joined at the centromere, that separate during cell division

    The Cell Cycle and Phases

    • Interphase
      • G1 phase: Cell grows and prepares for DNA synthesis
      • S phase: DNA replication occurs, creating two copies of each chromosome
      • G2 phase: Final preparation for division, like checking for DNA errors
    • Mitotic (M) Phase
      • Prophase: Chromosomes condense, nuclear membrane disintegrates, spindle fibers form
      • Metaphase: Chromosomes align at the middle of the cell, spindle fibers attach to centromeres
      • Anaphase: Sister chromatids are pulled apart by spindle fibers towards opposite poles
      • Telophase: Separated chromosomes reach poles, new nuclear membranes form around each set
    • Cytokinesis: Cell cytoplasm divides, forming two daughter cells
      • In animal cells, a cleavage furrow forms
      • In plant cells, a cell plate forms

    Chromosomes and Cell Division

    • Eukaryotic chromosomes are linear, while prokaryotic chromosomes are circular.
    • The Prokaryotic Chromosome:
      • A singular circular chromosome attached to the cell membrane
      • Contains a single, circular molecule of double-stranded DNA
      • Divides through binary fission
    • Eukaryotic Chromosomes:
      • Contain linear chromosomes within a nucleus
      • Contain long, linear molecules of DNA tightly coiled around protein complexes called histones, forming chromatin
      • Divides through mitosis

    Binary Fission

    • Asexual reproduction where a single-celled organism divides into two identical daughter cells
    • Common in bacteria and other prokaryotes

    Why Cells Divide

    • Growth and Development: To create more cells for larger size
    • Repair and Replacement: To replace damaged or dead cells

    Differentiation Between Vocab

    • Somatic Cell: Any cell other than reproductive cells
    • Germ Cells: Reproductive cells with half the number of chromosomes
    • Parent Cell: The original cell that divides into daughter cells
    • Daughter Cell: A new cell produced from a parent cell through division

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    Related Documents

    Chromosomes and Cell Division Notes PDF

    Description

    Explore the fundamental processes of meiosis II, including the separation of sister chromatids and the significance of sex chromosomes. Learn about DNA helicase and DNA polymerase roles in DNA replication, and the impact of telomeres on aging and cell lifespan. This quiz covers essential concepts in cell biology and genetics.

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