Cell Cycle and Interphase Overview
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Questions and Answers

What is the longest phase of the cell cycle during which the cell is not dividing?

  • Mitosis
  • Interphase (correct)
  • Meiosis
  • Cytokinesis

    • Which stage of interphase is primarily focused on DNA duplication?

  • Cytokinesis
  • G2 Stage
  • G1 Stage
  • S Stage (correct)

    • What type of cell division produces four daughter cells?

  • Cytokinesis
  • Interphase
  • Mitosis
  • Meiosis (correct)

    • During which phase does the duplication of centrioles occur?

    <p>G2 Stage</p> Signup and view all the answers

    Karyokinesis refers to which process in the cell cycle?

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

    Which type of cells undergoes mitosis?

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

    How many chromosomes are present at the end of the S stage of interphase in a human cell?

    <p>92</p> Signup and view all the answers

    Which of the following occurs during cytokinesis?

    <p>Cytoplasmic division</p> Signup and view all the answers

    What is the main outcome of mitosis?

    <p>Two daughter cells, each with 46 chromosomes</p> Signup and view all the answers

    During which phase of mitosis do chromosomes line up at the cell equator?

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

    In which type of cellular division does the nuclear envelope reappear after cytokinesis?

    <p>Both mitosis and meiosis</p> Signup and view all the answers

    How many chromosomes are present in each daughter cell after meiosis?

    <p>23 chromosomes</p> Signup and view all the answers

    What happens to homologous chromosomes during the zygotene phase of meiosis?

    <p>They pair and form bivalents</p> Signup and view all the answers

    What is the primary difference between mitosis and meiosis regarding the number of cells produced?

    <p>Meiosis produces four cells, mitosis produces two</p> Signup and view all the answers

    During anaphase of mitosis, what occurs to the sister chromatids?

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

    What is the function of the contractile ring during cytokinesis?

    <p>To create the cleavage furrow for cell separation</p> Signup and view all the answers

    What is the role of interphase in the cell cycle?

    <p>It prepares the cell for division.</p> Signup and view all the answers

    Which phase of the cell cycle represents the gap period prior to DNA synthesis?

    <p>G1 phase</p> Signup and view all the answers

    During which phase does karyokinesis occur?

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

    What distinguishes meiosis from mitosis?

    <p>Meiosis involves chromosomal reduction.</p> Signup and view all the answers

    Which of the following occurs during the S phase of interphase?

    <p>Duplicating the genetic material.</p> Signup and view all the answers

    How many total chromosomes are present in a human cell following the G2 phase?

    <p>92</p> Signup and view all the answers

    What is the outcome of mitosis regarding the genetic composition of daughter cells?

    <p>Daughter cells are identical to each other and the parent cell.</p> Signup and view all the answers

    What type of cell division primarily occurs in somatic cells?

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

    What is the main type of division that results in two daughter cells maintaining the original chromosome number?

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

    During which phase of mitosis do chromosomes achieve the highest degree of condensation?

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

    Which process describes the separation of sister chromatids during mitosis?

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

    What structure primarily facilitates the pulling apart of chromosomes during mitosis?

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

    What is the end result of meiosis in terms of chromosome number?

    <p>Each daughter cell has a haploid number of chromosomes</p> Signup and view all the answers

    Which stage of meiosis does not include an S phase during interphase?

    <p>1st Meiotic division</p> Signup and view all the answers

    What occurs to the nuclear envelope and nucleoli at the end of mitosis?

    <p>They reappear</p> Signup and view all the answers

    During which phase of the cell cycle is the synaptonemal complex formed?

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

    What are the end results of mitosis in terms of chromosome number for each daughter cell?

    <p>Each daughter cell has the same diploid number of chromosomes, which is 46.</p> Signup and view all the answers

    What is the significance of cytokinesis in cell division?

    <p>Cytokinesis is crucial as it physically separates the cytoplasm, leading to the formation of two distinct daughter cells.</p> Signup and view all the answers

    Describe the changes that occur to chromosomes during prophase.

    <p>During prophase, chromosomes condense and become visible, while the nuclear membrane breaks down and the mitotic spindle begins to form.</p> Signup and view all the answers

    What describes the primary difference between meiosis and mitosis?

    <p>The primary difference is that meiosis produces four haploid cells, while mitosis produces two diploid cells.</p> Signup and view all the answers

    In which phase of meiosis do homologous chromosomes form bivalents?

    <p>Homologous chromosomes form bivalents during the zygotene phase.</p> Signup and view all the answers

    What happens to the nuclear envelope during mitosis?

    <p>The nuclear envelope breaks down during prophase and reappears during telophase.</p> Signup and view all the answers

    What is meant by 'kinetochores' in the context of mitosis?

    <p>Kinetochores are protein structures that form on the centromere of chromosomes to facilitate their attachment to spindle microtubules.</p> Signup and view all the answers

    What is the role of the contractile ring during cytokinesis?

    <p>The contractile ring helps constrict the cell membrane, resulting in the physical separation of the two daughter cells.</p> Signup and view all the answers

    What occurs during the G2 phase of the cell cycle?

    <p>During the G2 phase, the cell continues to grow and duplicates its organelles in preparation for mitosis.</p> Signup and view all the answers

    Explain the difference between mitosis and meiosis in terms of daughter cells produced.

    <p>Mitosis produces two identical daughter cells, while meiosis results in four genetically diverse daughter cells.</p> Signup and view all the answers

    Define cytokinesis and its significance in cell division.

    <p>Cytokinesis is the cytoplasmic division of a parent cell into two daughter cells, crucial for completing the cell division process.</p> Signup and view all the answers

    What is the function of the S phase in the cell cycle?

    <p>The S phase is responsible for DNA synthesis and the duplication of chromosomes.</p> Signup and view all the answers

    Why is interphase considered the longest part of the cell cycle?

    <p>Interphase is the longest stage of the cell cycle as it encompasses growth, DNA replication, and preparation for division.</p> Signup and view all the answers

    Identify the primary role of karyokinesis during cell division.

    <p>Karyokinesis is the process of nuclear division that ensures the genetic material is equally distributed to daughter cells.</p> Signup and view all the answers

    Discuss the events that take place during the G1 phase of interphase.

    <p>During the G1 phase, the cell grows and carries out normal metabolic processes while preparing for DNA replication.</p> Signup and view all the answers

    How does meiosis contribute to genetic diversity?

    <p>Meiosis contributes to genetic diversity through processes like crossing over and independent assortment of chromosomes.</p> Signup and view all the answers

    What are the two main outcomes of mitosis in terms of daughter cell chromosome number?

    <p>Two daughter cells, each with the same diploid number of chromosomes (46 s chromosomes).</p> Signup and view all the answers

    In meiosis, what is the significance of the absence of an S phase between the two meiotic divisions?

    <p>It prevents DNA replication, ensuring that each of the four resulting cells has a haploid number of chromosomes (23 s chromosomes).</p> Signup and view all the answers

    During which phase of mitosis do chromosomes achieve their highest degree of condensation?

    <p>During metaphase, when chromosomes line up at the cell equator.</p> Signup and view all the answers

    How does the configuration of chromosomes differ between the zygotene phase of meiosis and the prophase of mitosis?

    <p>In zygotene, homologous chromosomes pair and form bivalents, while in prophase, chromosomes condense without pairing.</p> Signup and view all the answers

    What role do kinetochores play during anaphase in mitosis?

    <p>Kinetochores attach microtubules to chromosomes, enabling their separation and movement to opposite poles of the cell.</p> Signup and view all the answers

    What significant structural changes occur in the nucleus during prophase of mitosis?

    <p>The nuclear membrane disappears, and the nucleoli disintegrate, allowing the spindle apparatus to interact with chromosomes.</p> Signup and view all the answers

    Explain how cytokinesis differs between plant and animal cells.

    <p>In animal cells, a cleavage furrow forms, while in plant cells, a cell plate develops to divide the two daughter cells.</p> Signup and view all the answers

    During which meiotic phase do bivalents form, and what is their significance?

    <p>Bivalents form during the zygotene phase, crucial for genetic recombination and diversity.</p> Signup and view all the answers

    What defines the G1 phase of interphase in terms of cellular activity?

    <p>The G1 phase involves cell growth and preparation for DNA replication.</p> Signup and view all the answers

    How many daughter cells are produced at the end of mitosis, and what is their chromosome number compared to the original cell?

    <p>Mitosis results in two daughter cells, each with the same chromosome number as the original cell, which is 46 in humans.</p> Signup and view all the answers

    Explain the significance of the S phase during interphase.

    <p>The S phase is crucial for DNA duplication, ensuring each daughter cell receives an identical set of chromosomes.</p> Signup and view all the answers

    What is karyokinesis and how does it differ from cytokinesis?

    <p>Karyokinesis is the division of the nucleus, while cytokinesis is the division of the cytoplasm.</p> Signup and view all the answers

    In the context of meiosis, what role do homologous chromosomes play during prophase I?

    <p>Homologous chromosomes pair up to form bivalents, allowing genetic recombination through crossover events.</p> Signup and view all the answers

    Describe the outcome of meiosis in terms of daughter cells produced and their genetic composition.

    <p>Meiosis produces four genetically diverse daughter cells, each with half the chromosome number of the parent cell.</p> Signup and view all the answers

    Identify the changes occurring to chromosomes during anaphase of mitosis.

    <p>During anaphase, sister chromatids are pulled apart to opposite poles of the cell.</p> Signup and view all the answers

    What is the primary difference between somatic cells and germ cells concerning their division processes?

    <p>Somatic cells undergo mitosis, while germ cells undergo meiosis to produce gametes.</p> Signup and view all the answers

    Study Notes

    Cell Cycle

    • The cell cycle is a series of events that occur within a cell, leading to its growth and division into two daughter cells.
    • The cell cycle is comprised of two phases:
      • Interphase: This is the longest part of the cell's life cycle where the cell is not actively dividing.
      • Cell division

    Interphase

    • This phase is the period between two successive cell divisions.
    • It is further subdivided into three stages:
      • G1 (first gap) stage: This is the period between the end of mitosis and the beginning of the S stage. During this stage, the newly formed daughter cell grows and prepares for DNA replication.
      • S (synthesis) stage: During this stage, chromosomal duplication takes place. Each of the 46 S-chromosomes in the cell is duplicated resulting in 92 S-chromosomes.
      • G2 (second gap) stage: This is the period between the end of the S stage and the beginning of mitosis. Here, the cell continues to grow and prepares for cell division, also the centrioles are duplicated.

    Cell Division

    • This is the process by which a single cell divides to produce two or more daughter cells.
    • Two main types of cell division are:

      Mitosis

      • This is a type of cell division that occurs in somatic cells. It results in two daughter cells, each containing the same number of chromosomes as the parent cell (46 S chromosomes).
      • The process occurs in four stages:
        • Prophase:
          • The nuclear membrane breaks down.
          • The nucleolus disintegrates.
          • The spindle fibers form between the two centrioles as they move apart.
          • The chromosomes condense and thicken becoming visible under the microscope.
        • Metaphase:
          • The chromosomes align along the cell equator.
          • They attain their highest degree of condensation.
          • This stage is ideal for karyotyping, which is a process used to analyze chromosomes.
        • Anaphase:
          • The centromere of each chromosome splits.
          • Each sister chromatid is now considered a separate chromosome, resulting in 92 s chromosome in total.
          • The separated chromosomes are pulled apart by the spindle fibers towards the opposite poles of the cell.
        • Telophase:
          • The nuclear envelope reforms around each set of chromosomes at the poles of the cell.
          • The spindle fibers disintegrate.
          • The chromosomes uncoil and become less visible.
          • The nucleoli reappear within each nucleus.
      • Cytokinesis:
        • The division of the cytoplasm, which occurs simultaneously with telophase.
        • A cleavage furrow forms between the two nuclei.
        • The cleavage furrow deepens until the two daughter cells are completely separated.

      Meiosis

      • This is a type of cell division that occurs in germ cells (sperm and egg cells).
      • It results in four daughter cells, each containing half the number of chromosomes as the parent cell (23 S chromosomes).
      • This process involves two consecutive cell divisions:
        • Meiosis I:
          • Prophase I: chromosomes condense, homologous chromosomes pair up, crossing over occurs.
          • Metaphase I: paired chromosomes line up.
          • Anaphase I: homologous chromosomes separate and move to opposite poles.
          • Telophase I: daughter cells are formed.
        • Meiosis II: Similar to mitosis, daughter cells divide again to form four haploid gametes.
    • It's important to note: there is NO S stage in the interphase between the two meiotic divisions.

    Cell Cycle and Cell Division

    • The cell cycle is a sequence of events that occur in a cell, including growth and division, resulting in two daughter cells.

    Interphase (Resting Stage)

    • The longest phase of the cell cycle where the cell is not dividing.
    • Interphase is divided into three stages: G1, S, and G2.

    G1 (1st Gap) Stage

    • Occurs between the end of mitosis and the beginning of the S stage.
    • The newly formed daughter cell grows.

    S (Synthesis) Stage

    • Stage of chromosome duplication.
    • Each identical pair of S-chromosomes forms one d-chromosome.
    • After growth, cells duplicate centrioles.
    • The number of chromosomes changes from 46 S-chromosomes to 92 S-chromosomes and then to 46 d-chromosomes.

    G2 (2nd Gap) Stage

    • Occurs between the end of the S stage and the beginning of the next mitosis.
    • The cell prepares for division.

    Cell Division

    • The process of dividing the cell into two daughter cells.

    Karyokinesis

    • Nuclear division that divides the genetic material within the nucleus.

    Cytokinesis

    • Cytoplasmic division that divides the cytoplasm.

    Types of cell division

    Mitosis (Indirect Cell Division)

    • Occurs in somatic cells (all body cells except eggs and sperms).
    • Produces two daughter cells with the same number of chromosomes as the mother cell (46 S-chromosomes, diploid number).

    Meiosis (Reduction Cell Division)

    • Occurs in germ cells of the testes and ovaries.
    • Produces four daughter cells, each with half the number of chromosomes of the mother cell (23 S-chromosomes, haploid number).

    Mitosis Stages

    • Divided into four stages: prophase, metaphase, anaphase, and telophase.

    Prophase

    • Fragmentation of the endoplasmic reticulum (ER), Golgi apparatus, and disassembly of the cytoskeleton.
    • Formation of the mitotic spindle. Microtubules arise from pairs of centrioles (MTOCs), causing:
      • Formation of an eccentric spindle.
      • Gradual elongation of the cell.
    • The nuclear membrane breaks down.
    • The nucleoli disintegrate.
    • The spindle becomes central.
    • D-chromosomes lie in the inter-tubular spaces of the spindle.
    • Chromosomes condense, and kinetochores appear.

    Metaphase

    • Chromosomal microtubules form, and d-chromosomes:
      • Become arranged at the cell equator.
      • Achieve the highest degree of condensation.
      • Ideal stage for karyotyping.

    Anaphase

    • Chromosomes split at the centromere (46 d-chromosomes → 92 S-chromosomes).
    • Two identical sets of S-chromosomes (2 x 46 S-chromosomes) are arranged.
    • Each set of S-chromosomes moves to opposite poles of the cell, pulled by microtubules.

    Telophase

    • Cytokinesis forms a contractile ring, leading to the formation of a cleavage furrow. The furrow deepens until the two daughter cells separate.
    • The nuclear envelope and nucleoli reappear.
    • Two daughter cells are produced, each with 46 S-chromosomes.

    Meiosis Stages

    • Divided into two divisions: first meiotic division and second meiotic division.

    • The second meiotic division is similar to mitosis.

    • There is no S stage in the interphase between the two meiotic divisions.

    First Meiotic Division

    • Divided into four stages: Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis.
    Leptotene Phase
    • D-chromosomes appear as thin threads.
    Zygotene Phase
    • Homologous d-chromosomes pair with the formation of a synaptonemal complex, forming bivalents.

    Cell Cycle

    • The cell cycle is a series of events that take place in a cell, involving cell growth and division to produce two daughter cells.

    Interphase (Resting Stage)

    • The longest part of the cell's life cycle, and the cell is not dividing.
    • Composed of three stages: G1, S, and G2.

    G1 Stage (First Gap)

    • Gap between the end of mitosis and the beginning of the S stage.
    • Newly formed daughter cells grow.
    • DNA duplication occurs.

    S Stage (Synthesis)

    • Stage of chromosome duplication.
    • Each identical pair of S-chromosomes forms one d-chromosome.
    • Centrioles duplicate.
    • The number of chromosomes increases from 46 S-chromosomes to 92 S-chromosomes, and then back down to 46 d-chromosomes after duplication.

    G2 Stage (Second Gap)

    • Gap between the S stage and the beginning of the next mitosis.
    • Cells continue to grow.

    Cell Division

    • Occurs after interphase and results in two daughter cells.
    • Two main types of division: mitosis and meiosis.

    Mitosis

    • The type of division that produces two daughter cells, each with the same number of chromosomes as the mother cell (46 s-chromosomes).
    • Stages include prophase, metaphase, anaphase, and telophase.

    Prophase

    • Fragmentation of the endoplasmic reticulum (ER), Golgi apparatus, and disassembly of the cytoskeleton.
    • Mitotic spindle formation: Microtubules form from pairs of centrioles (MTOCs).
    • Nuclear membrane breaks down.
    • Nucleoli disintegrate.

    Metaphase

    • The spindle becomes central.
    • D-chromosomes lie in the inter-tubular spaces of the spindle.
    • D-chromosomes become more condensed with the appearance of kinetochores.
    • Chromosomal microtubules form.
    • D-chromosomes:
      • Become arranged at the cell equator.
      • Achieve the highest degree of condensation.
      • This stage is ideal for karyotyping.

    Anaphase

    • Splitting of chromosomes at the centromere (46 d-chromosomes → 92 s-chromosomes arranged in two identical sets (2 x 46 s-chromosomes)).
    • Separation: Each set of s-chromosomes moves to the opposite pole of the cell, pulled by microtubules.

    Telophase

    • Cytokinesis:
      • Formation of a contractile ring.
      • Formation of a cleavage furrow, which deepens gradually until separation of the two daughter cells.
    • Nuclear envelope and nucleoli reappear.
    • Two daughter cells are produced, each with 46 s-chromosomes.

    Meiosis

    • The type of division that produces four cells, each with half (haploid) the number of chromosomes of the mother cell (23 s-chromosomes).
    • First meiotic division:
      • Leptotene phase: D-chromosomes appear as thin threads.
      • Zygotene phase: Homologous d-chromosomes pair, forming a synaptonemal complex called bivalents.
    • Second meiotic division: Similar to mitosis.

    Key Differences Between Mitosis and Meiosis

    Feature Mitosis Meiosis
    Daughter cells Two daughter cells Four daughter cells
    Chromosome # Same as mother cell (diploid) Half of mother cell (haploid)
    Cell type Somatic cells (body cells except gametes) Germ cells of testis and ovary (gametes)
    S Stage Present between divisions Absent between first and second meiotic divisions

    Cell Cycle

    • The cell cycle is a series of events involving cell growth and division
    • It produces two daughter cells.
    • The cycle consists of Interphase (resting stage) and Cell division.

    Interphase

    • Longest part of the cell's life cycle.
    • The cell isn't dividing.
    • Period between two successive cell divisions.

    Stages of Interphase

    • G1 (1st gap) stage: Gap between the end mitosis and the beginning of S stage. New daughter cells grow.
    • S (synthesis stage): Stage of chromosome duplication.
    • G2 (2nd gap) stage: Gap between the end of S stage and the beginning of the next mitosis.

    Cell Division

    • Divided into two main processes: Karyokinesis (nuclear division) and Cytokinesis (cytoplasmic division)
    • Karyokinesis also has two types: Mitosis and Meiosis.

    Mitosis

    • Indirect cell division.
    • Occurring in somatic cells (all body cells excluding egg and sperm).
    • Produces two identical daughter cells with the same number of chromosomes as the mother cell (46 s- chromosomes = diploid number).
    • Stages of Mitosis: Prophase, Metaphase, Anaphase, Telophase.

    Meiosis

    • Reduction cell division occurring in germ cells (testis and ovary).
    • Produces four daughter cells, each with half the number of chromosomes as the mother cell (23 s - chromosomes = haploid number).
    • There are two meiotic divisions. The second one is similar to mitosis.
    • Interphase between meiotic divisions does not include the S stage.

    Prophase (Mitosis)

    • Fragmentation of ER, Golgi, and disassembly of cytoskeleton.
    • Mitotic spindle formation: Continuous microtubules arise from pairs of centrioles (MTOCs).
    • Nuclear membrane breaks down.
    • Nucleoli disintegrate.
    • Spindle becomes central.
    • D-chromosomes lie in the inter-tubular spaces of the spindle.
    • D-chromosomes condense with appearance of kinetochores.

    Metaphase (Mitosis)

    • Chromosomal microtubules form.
    • D-chromosomes become arranged at the cell equator.
    • D-chromosomes reach maximum condensation.
    • This phase is ideal for karyotyping.

    Anaphase (Mitosis)

    • Chromosomes split at the centromere (46 d-chromosomes become 92 s-chromosomes).
    • Two identical sets of s-chromosomes are arranged (2 x 46 s- chromosomes).
    • Each set of s-chromosomes moves to the opposite pole of the cell, driven by microtubules.

    Telophase (Mitosis)

    • Cytokinesis:
      • Contractile ring forms.
      • Cleavage furrow deepens until the separation of the two daughter cells.
    • Nuclear envelope and nucleoli reappear.
    • The end result is the production of two daughter cells, each containing 46 s-chromosomes.

    Leptotene Phase (Meiosis)

    • D- chromosomes appear as thin threads.

    Zygotene Phase (Meiosis)

    • Homologous D-chromosomes pair with the formation of the synaptonemal complex.
    • These pairs are called bivalents.

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