Mitosis and Cell Cycle Quiz
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Questions and Answers

What occurs during anaphase of mitosis?

  • Nuclear membranes reassemble around nuclei.
  • Microtubules lengthen to move chromosomes.
  • Chromosomes are pulled to opposite poles. (correct)
  • Sister chromatids condense into chromatin.

    • Which phase of mitosis sees the nuclear membrane disappear?

  • Interphase
  • Prophase (correct)
  • Telophase
  • Anaphase

    • What structure forms during cytokinesis in animal cells?

  • Polar microtubules
  • Nuclear membrane
  • Chromatin
  • Cleavage furrow (correct)

    • At what stage do chromosomes align at the equator of the cell?

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

    What happens to sister chromatids after they are separated during anaphase?

    <p>They are called chromosomes.</p> Signup and view all the answers

    Which option describes telophase in mitosis?

    <p>New nuclear membranes form around chromosomes.</p> Signup and view all the answers

    What process follows mitosis to create two separate cells?

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

    What is the arrangement of chromatin during interphase?

    <p>Not visible and thread-like.</p> Signup and view all the answers

    What is the role of telomeres in the cell cycle?

    <p>They act as a molecular clock for cellular aging.</p> Signup and view all the answers

    What occurs during the process of metastasis in cancer?

    <p>Cancer cells lose attachment to neighboring cells.</p> Signup and view all the answers

    How many cellular divisions take place within the average human per day?

    <p>About 150 million.</p> Signup and view all the answers

    What is the major characteristic of cancer cells compared to normal cells?

    <p>Cancer cells divide uncontrollably.</p> Signup and view all the answers

    What happens to telomeres each time a normal cell divides?

    <p>They shorten.</p> Signup and view all the answers

    What type of signals regulate cellular division?

    <p>Internal protein interactions and external factors.</p> Signup and view all the answers

    At what age is the telomere length of a child compared to that of a 70-year-old?

    <p>Longer than that of a 70-year-old.</p> Signup and view all the answers

    What is the characteristic of advanced cancer cells regarding their ability to divide?

    <p>They continue to divide despite healthy cells around them.</p> Signup and view all the answers

    What is the result of meiosis I?

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

    What does interkinesis refer to in the process of meiosis?

    <p>The stage following telophase I.</p> Signup and view all the answers

    What is true about the daughter cells produced after meiosis I?

    <p>Each contains one member of each chromosome pair.</p> Signup and view all the answers

    Which statement about meiosis II is accurate?

    <p>It is identical to the mitotic phases.</p> Signup and view all the answers

    Which of the following best describes segregation during meiosis I?

    <p>It refers to the separation of bivalents.</p> Signup and view all the answers

    What characterizes telophase I in meiosis?

    <p>It is when the cytoplasm divides into two cells.</p> Signup and view all the answers

    What happens to the chromosome structure during Anaphase I?

    <p>Bivalents are separated into separate homologues.</p> Signup and view all the answers

    What role does telomerase play in cancer cells?

    <p>It allows continuous division of cancer cells.</p> Signup and view all the answers

    Which cancer treatment option primarily targets rapidly dividing cells?

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

    What is the process of senescence in the context of cellular biology?

    <p>Biological aging and loss of the ability to divide.</p> Signup and view all the answers

    Which treatment method involves the direct removal of cancer cells from a tumor site?

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

    How does radiation therapy work in cancer treatment?

    <p>Through the use of gamma or x-rays to destroy cells.</p> Signup and view all the answers

    What is the primary goal of developing drugs that block telomerase action in cancer cells?

    <p>To induce senescence and limit cell division.</p> Signup and view all the answers

    Which cancer treatment method is NOT mentioned as one of the three main options?

    <p>Gene Therapy</p> Signup and view all the answers

    What is a characteristic of cancer cells that differentiate them from normal cells?

    <p>They can divide continuously.</p> Signup and view all the answers

    What is the primary structural unit of chromatin?

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

    During which phase of the cell cycle are chromosomes visible as distinct structures?

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

    What holds sister chromatids together?

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

    What role does the kinetochore play in mitosis?

    <p>It acts as a docking site for microtubules.</p> Signup and view all the answers

    What does chromatin become when the cell prepares for division?

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

    Which statement about sister chromatids is correct?

    <p>They are always identical.</p> Signup and view all the answers

    Which feature is NOT associated with chromatin during interphase?

    <p>Visible chromosomes</p> Signup and view all the answers

    What distinguishes chromosomes from chromatin?

    <p>Chromosomes are condensed and distinct.</p> Signup and view all the answers

    What does the centromere facilitate during cell division?

    <p>Separation of sister chromatids</p> Signup and view all the answers

    What is the state of DNA in the nucleus during interphase?

    <p>Uncoiled and organized as chromatin</p> Signup and view all the answers

    What is the consequence of nondisjunction during meiosis?

    <p>One daughter cell may have more chromosomes than normal.</p> Signup and view all the answers

    In the context of nondisjunction, what does the term 'trisomy' refer to?

    <p>The presence of three copies of a chromosome.</p> Signup and view all the answers

    If a zygote forms with 45 chromosomes, what type of nondisjunction condition could have occurred?

    <p>Monosomy condition.</p> Signup and view all the answers

    What chromosomal abnormality is associated with Down syndrome?

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

    Which of the following conditions represents a monosomy?

    <p>Turner syndrome.</p> Signup and view all the answers

    Which of the following statements is true regarding nondisjunction?

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

    What is the result of nondisjunction occurring during anaphase of meiosis I?

    <p>Two homologous chromosomes move to the same pole.</p> Signup and view all the answers

    What characterizes aneuploidy?

    <p>Chromosome counts of 45 or 47.</p> Signup and view all the answers

    Which of the following is a risk associated with nondisjunction during meiosis?

    <p>Gametes may have an altered number of chromosomes.</p> Signup and view all the answers

    What is the result when two sister chromatids fail to separate during anaphase of meiosis II?

    <p>One daughter cell has an extra chromosome and another is missing one.</p> Signup and view all the answers

    Study Notes

    Unit C: Cells, Chromosomes and DNA

    • Chapters 17 and 20 cover cell division and molecular genetics (DNA)
    • Cell division is crucial for growth, maintenance, and repair in all life forms.
    • There are approximately 150 billion cell divisions daily in the human body, originating from a single fertilized egg.
    • Mitosis is the process of asexual division for growth and repair, maintaining chromosome number.
    • Meiosis creates gametes (germ cells) for sexual reproduction and reduces the chromosome number by half.

    Cell Division

    • Chapter 17 discusses the cell cycle
    • Cell cycle: the cell cycle, mitosis, and meiosis
    • Chapter 17, page 556-595 in Metro Biology 30
    • 17.1, pages 558-563 (The Cell Cycle)

    Why Divide?

    • All life depends on the ability to grow, maintain, and repair cells.
    • Cells arise from pre-existing cells.
    • In a human, 100 trillion cells originate from a single fertilized egg.
    • Cell division ensures accurate reproduction of genetic and cellular matter.

    Mitosis

    • Responsible for body (somatic) cell growth, repair, and maintenance;
    • Maintains the normal chromosome number (2n)
    • Considered a form of asexual cellular division.

    Meiosis

    • Creates sex cells (gametes) for sexual reproduction - germ cells
    • Reduces the chromosome number (2n to 1n) in gametes
    • Enables genetic variety through crossing over in prophase I

    Genetic Material in Eukaryotes

    • Genetic information is found within the nucleus as DNA in chromatin.
    • Chromatin is a complex of DNA and proteins (histones).
    • DNA is tightly wrapped around histone proteins, forming nucleosomes.
    • DNA is compact in the cell, fitting inside a nucleus much smaller than the DNA itself: ~150 km string in 5 micrometer diameter nucleus.
    • Chromatin (uncoiled, thin strands of DNA) vs. Chromosomes (condensed structures of DNA)
    • Chromatin condenses into visible chromosomes during cell division.

    Chromatin vs. Chromosomes

    • DNA is super-coiled to form chromatin or chromosomes, depending on the cell cycle stage.
    • Chromatin (interphase): uncondensed DNA
    • Chromosomes (mitosis): condensed into visible, distinct structures.
    • Nucleosomes are the basic structural units of chromatin, consisting of DNA coiled around histone proteins.

    Chromosome Structure

    • Replicated chromosomes are called sister chromatids, attached at a centromere.
    • Each chromatid identical to its sister chromatid, though may have different alleles.
    • The centromere is the region of the chromosome where sister chromatids attach.

    Centromeres and Kinetochores

    • The centromere is a specialized region of a chromosome that holds the sister chromatids together.
    • Kinetochores are protein structures located on the centromeres.
    • Kinetochores serve as "docking sites" on the centromeres for microtubules of the mitotic spindle.
    • Microtubules are involved in chromosome movement during cell division.

    Chromosome Number

    • Chromosome numbers vary considerably among different species.
    • Even closely related organisms can have markedly different chromosome numbers.
    • Humans have 46 chromosomes.

    Ploidy

    • Ploidy refers to the number of chromosome sets in a cell.
    • Haploid (n): single set of chromosomes (gametes)
    • Diploid (2n): two sets of chromosomes (somatic cells)
    • Some organisms are polyploid (more than two sets of chromosomes)

    Genes on Chromosomes

    • Genes are sections of DNA that contain instructions to make proteins.
    • Genes are located at specific locations on chromosomes called loci.
    • Alleles are different forms of a gene.

    The Cell Cycle - Interphase

    • Interphase is the longest phase of the cell cycle (approx. 90%).
    • It consists of three stages: G1 (growth), S (DNA synthesis/replication), and G2 (growth).
    • Chromosomes are duplicated during the S phase, though they are still called chromosomes (because they are attached at the centromere).

    Gap 1 (G₁), Synthesis (S), and Gap 2 (G₂) Phases of Interphase

    • G1: growth and metabolic activity
    • S: DNA replication and chromosome duplication
    • G2: preparation for mitosis, growth

    The Cell Cycle - Mitosis & Cytokinesis

    • The M phase includes mitosis and cytokinesis.
    • Mitosis: the process of nuclear division
    • Four phases of mitosis: prophase, metaphase, anaphase, and telophase;
    • Cytokinesis: The division of the cytoplasm to form two separate daughter cells.

    Microtubules, and Mitotic Spindle

    • Microtubules form the mitotic spindle, a structure of protein fibers responsible for organizing and moving chromosomes during mitosis and meiosis.
    • Microtubules are assembled during prophase.
    • Microtubules are disassembled during anaphase.

    Plant Toxins Interrupt Microtubules

    • Colchicine: derived from autumn crocus (Colchicinium autumnale), binds to tubulin subunits and disrupts microtubule assembly, preventing cell division. Used medically in gout treatment.
    • Taxol: derived from western yew (Taxus brevifolia), an anti-cancer medicine, which prevents microtubule disassembly, which halts cell division.

    Phases of Mitosis

    • Based on chromosome arrangement and cell structures.

    Prophase (Early & Late)

    • Chromatin condenses into chromosomes.
    • Nucleoli disappear.
    • Nuclear envelope fragments.
    • Centrosomes move to opposite poles and the mitotic spindle forms.
    • In late prophase, microtubules attach to kinetochores of the sister chromatids.

    Metaphase

    • Chromosomes align midway on mitotic plate (equator).

    Anaphase

    • Centromeres divide, separating sister chromatids.
    • Chromatids move to opposite poles.

    Telophase

    • Chromosomes reach opposite poles.
    • Nuclear envelopes reform—2 new nuclei form.
    • Chromosomes begin to decondense.
    • Cell furrow begins to develop. Cellular division is completed through cytokinesis.

    Cytokinesis

    • Cytoplasm divides, forming two identical daughter cells.
    • In animals, a cleavage furrow forms.
    • In plants, a cell plate forms to construct new cell walls.

    Mitosis in Onion Cells

    • Most onion root cells are in interphase during cell observation.

    Microscopic Observations of Mitosis

    • Pictures/micrographs of the various stages are included.

    Plant Mitosis

    • Plant cells lack centrioles.
    • Plant cytokinesis involves cell plate formation.

    You Try: Onion Root Slides

    • Slides of different phases of mitosis in onion root cells

    Chromosome Number: Ploidy (Again)

    • For humans, haploid (n) number = 23, diploid (2n) = 46

    Meiosis I

    • Separation of homologous chromosome pairs.
    • Prophase I: Homologous chromosomes pair and may exchange segments (crossing over). Tetrads form. Homologues are separated.
    • Metaphase I: Tetrads line up at the metaphase plate.
    • Anaphase I: Homologous chromosomes separate and move to opposite poles.
    • Telophase I: Chromosomes arrive at poles, the nuclear membrane re-forms, and the cell divides through cytokinesis to form two daughter cells—each haploid, each with a (n) chromosome number.

    Interkinesis

    • Short period between meiosis I and meiosis II (No DNA Replication again).

    Meiosis II

    • Similar to mitosis, but separates sister chromatids
    • Prophase II: Duplicated chromosomes condense and nuclear envelopes disintegrate.
    • Metaphase II: Duplicated chromosomes line up along each cell's metaphase plate.
    • Anaphase II: The sister chromatids separate and migrate to opposite poles.
    • Telophase II: Nuclear Envelopes reform. The cell divides again via cytokinesis, resulting in 4 haploid daughter cells.

    Gametogenesis: Sperm & Egg Production in Humans

    • Meiosis produces gametes (sex cells–ova and sperm).

    Timing of Meiosis for Female Gametogenesis

    • First meiotic division initiated in the embryo but stops at prophase I;
    • Secondary meiotic division (Meiosis II) starts after puberty (and is arrested again until fertilization).

    Male Gametogenesis

    • Meiosis I creates two secondary spermatocytes (haploid);
    • Meiosis II creates 4 spermatids (haploid), which develop into sperm.

    Summary of Gametogenesis

    • Details about timing and processes of oogenesis and spermatogenesis – diagrams provided
    • Summary of gametogenesis in plants (including alternation of generations)

    Mitosis vs. Meiosis

    • Mitosis: produces genetically identical daughter cells for growth, repair, and asexual reproduction.
    • Meiosis: produces genetically diverse gametes, reducing the chromosome number.

    Origins of Genetic Variation

    • Differences in meiosis, including independent assortment (random orientation at Metaphase I) and crossing-over (exchange of genetic material at Prophase I).
      • Numbers for possible chromosome combinations resulting from multiple independent assortment events (for humans).

    Abnormal Meiosis - Nondisjunction

    • The failure of chromosomes to segregate properly during meiosis (either during meiosis I or meiosis II). Possible outcomes include trisomy or monosomy conditions.

    • The effects of nondisjunctions

    • Common nondisjunction-related syndromes, including Down syndrome (trisomy 21), Turner syndrome (monosomy X), and Klinefelter syndrome (XXY).

    • Karyotyping: used to diagnosing nondisjunction-related disorders

    Karyotyping

    • Karyotyping is a technique used to visualize and analyze the chromosomes of an organism—used in diagnosing disorders.
    • Steps involved.
    • Analyzing banding patterns, satellite/centromere positions.

    Human Karyotypes

    • Diagrams depicting normal human karyotypes—autosomes, sex chromosomes.

    Additional Information:

    • Note that the information about the symptoms and frequency of genetic disorders are not to be memorized.
    • Included are learning activities and resources to encourage active learning.

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    Unit C: Cells, Chromosomes and DNA PDF

    Description

    Test your knowledge on the stages of mitosis and the cell cycle with this quiz. From anaphase to cytokinesis, explore key concepts such as chromatin arrangement, telomere function, and cancer cell characteristics. Perfect for students studying biology and cell division.

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