Cell Cycle and Mitosis Overview
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Cell Cycle and Mitosis Overview

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Questions and Answers

Which phase involves the replication of DNA?

  • G1 phase
  • G2 phase
  • M phase
  • S phase (correct)

    • What is the function of the checkpoint in G1 phase?

  • Ensuring sufficient cell growth (correct)
  • Verifying DNA replication
  • Initiating cytokinesis
  • Checking chromosome alignment

    • In which phase of mitosis do the chromosomes line up in the middle of the cell?

  • Prophase
  • Anaphase
  • Telophase
  • Metaphase (correct)

    • During which phase do chromosomes move to opposite ends of the cell?

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

    What occurs during cytokinesis?

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

    Which phase is described as a resting phase for cells?

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

    What is the main purpose of meiosis?

    <p>Creation of gametes</p> Signup and view all the answers

    What happens during telophase?

    <p>Nuclei begin forming around separated chromosomes</p> Signup and view all the answers

    What process follows telophase II in meiosis?

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

    During which phase of meiosis do the chromatids separate?

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

    What is the primary product of spermatogenesis?

    <p>Four haploid sperm cells</p> Signup and view all the answers

    What is the main difference between metaphase I and metaphase II?

    <p>Chromosomes are not in homologous pairs in metaphase II</p> Signup and view all the answers

    What initiates the separation of homologous chromosomes?

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

    When does the number of chromosomes become haploid during gametogenesis?

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

    How many chromatids are present in prophase I when n = 23?

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

    Which of the following accurately describes oogenesis?

    <p>Usually produces one mature egg per menstrual cycle</p> Signup and view all the answers

    How many chromosomes do human sperm and egg cells contain?

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

    What is the primary purpose of meiosis in terms of chromosome number?

    <p>To reduce the number of chromosomes</p> Signup and view all the answers

    In which phase of meiosis does crossing over occur?

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

    How are chromosomes arranged during Metaphase I of meiosis?

    <p>In pairs</p> Signup and view all the answers

    What happens during Anaphase I of meiosis?

    <p>Homologous chromosomes move to opposite poles</p> Signup and view all the answers

    What is NOT a characteristic of Prophase II?

    <p>Homologous pairing occurs</p> Signup and view all the answers

    What is the end result of Telophase I?

    <p>Two newly formed nuclei</p> Signup and view all the answers

    During which phase of meiosis do the chromatids get pulled away?

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

    What are totipotent stem cells capable of giving rise to?

    <p>Any of the 220 cell types in the embryo</p> Signup and view all the answers

    Which pathway is triggered by internal cell damage during apoptosis?

    <p>Intrinsic pathway</p> Signup and view all the answers

    What is the primary outcome of the execution phase in apoptosis?

    <p>Fragmentation of DNA and degradation of proteins</p> Signup and view all the answers

    What is a key difference between necrosis and apoptosis?

    <p>Necrosis leads to inflammation; apoptosis does not.</p> Signup and view all the answers

    What type of stem cells are found in various tissues like muscle, skin, and liver?

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

    Which initiator caspase is activated during the intrinsic pathway of apoptosis?

    <p>Caspase-9</p> Signup and view all the answers

    What happens during the loss of membrane integrity in necrosis?

    <p>Cell membrane is disrupted, leading to swelling</p> Signup and view all the answers

    During which phase of meiosis do cells have the least amount of chromosomal material?

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

    What external cue can influence stem cell differentiation?

    <p>Environmental temperature</p> Signup and view all the answers

    What process restores the diploid number of chromosomes in an organism?

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

    What behavior do cancer cells exhibit in terms of division?

    <p>They do not stop dividing and are uncontrolled.</p> Signup and view all the answers

    Which of the following is a risk factor for the development of cancer cells?

    <p>Exposure to toxins and radiation</p> Signup and view all the answers

    How do cancer cells interact with healthy cells regarding nutrient supply?

    <p>They divert blood vessels to themselves, taking nutrients from healthy cells.</p> Signup and view all the answers

    What is the role of transcription factors in cell differentiation?

    <p>They determine which genes are expressed in a cell.</p> Signup and view all the answers

    What type of cues influence stem cell differentiation?

    <p>Internal and external cues</p> Signup and view all the answers

    Which type of cell is an example of a differentiated cell?

    <p>Neural cell</p> Signup and view all the answers

    Study Notes

    Interphase

    • Cell growth and DNA replication occur in three stages: G1, S, and G2.
    • G1: Cell increases in size and prepares for DNA replication.
    • S: DNA is replicated.
    • G2: Cell continues to grow and prepares for mitosis.

    Checkpoints

    • Three checkpoints ensure proper cell division.
    • G1 checkpoint: Monitors cell size and DNA damage.
    • G2 checkpoint: Verifies accurate DNA replication during S phase.
    • M checkpoint: Checks chromosomes are aligned and attached to the spindle correctly during metaphase.

    G0 Phase

    • Cells in the resting phase, performing cell functions but not dividing.
    • Some cells enter G0 temporarily due to lack of resources.
    • Others remain in G0 permanently, never entering mitosis (e.g., neurons).

    Mitosis

    • Mitosis involves four stages: Prophase, Metaphase, Anaphase, and Telophase (PMAT).
    • Prophase: Chromosomes condense and become visible; nuclear membrane begins to disappear.
    • Metaphase: Chromosomes align at the cell's equator, attached to spindles (microtubules).
    • Anaphase: Chromatids separate and move towards opposite poles pulled by spindle fibers.
    • Telophase: Two new nuclei are formed on opposite sides of the cell, chromosomes are at the poles, and the cell divides.
    • Cytokinesis, following PMAT, completes cell division by splitting the cytoplasm.

    Meiosis

    • Meiosis produces gametes (sperm and egg cells).
    • Meiosis involves two cell divisions (Meiosis I and Meiosis II).
    • Before meiosis, DNA replication (interphase) occurs, doubling the number of chromosomes to 46 chromosomes and 92 chromatids.
    • Meiosis I:
      • Prophase I: Chromosomes condense with their homologous pair. Crossing over occurs.
      • Metaphase I: Homologous pairs line up at the cell's equator.
      • Anaphase I: Homologous pairs are separated and pulled towards the poles.
      • Telophase I: Two new nuclei are formed, each with half the number of chromosomes.
      • Cytokinesis: Cell divides into two.
    • Meiosis II:
      • Prophase II: Spindles begin to form.
      • Metaphase II: Chromosomes line up in a single file line at the cell's equator.
      • Anaphase II: Sister chromatids are separated and pulled towards poles by spindles.
      • Telophase II: Two new nuclei are formed in each of the cells, resulting in four daughter cells with half the number of chromosomes.
      • Cytokinesis: Cell divides into two.

    Comparing Metaphase I and Metaphase II

    • Metaphase I: Chromosomes align in pairs.
    • Metaphase II: Chromosomes align in a single file line.

    Comparing Anaphase I and Anaphase II

    • Anaphase I: Homologous pairs are separated.
    • Anaphase II: Sister chromatids are separated.

    Number of Bivalents, Chromosomes, and Chromatids in Prophase I

    • n = 23 chromosomes
    • 2n = 46 chromosomes
    • 4n = 92 chromatids

    Gametogenesis Stages: Homologous Chromosome Separation and Haploid Condition

    • Homologous chromosomes are separated during Anaphase I.
    • Sister chromatids are separated during Anaphase II.
    • Cells become haploid (having half the number of chromosomes) in Telophase II.

    Spermatogenesis vs. Oogenesis

    • Location: Spermatogenesis in testes, Oogenesis in ovaries.
    • Start time: Spermatogenesis at puberty, Oogenesis during fetal development.
    • End time: Spermatogenesis throughout life, Oogenesis ends at menopause.
    • Duration: Spermatogenesis continuous, Oogenesis cyclical and can take years.
    • Primary Products: Spermatogenesis produces four sperm cells, Oogenesis produces one egg cell and polar bodies.
    • Cytokinesis: Spermatogenesis - equal division of cytoplasm; Oogenesis - unequal division, egg receives most cytoplasm.
    • Cell Output: Spermatogenesis - millions of sperm per day; Oogenesis - usually one mature egg per menstrual cycle.
    • Timing of Meiosis: Spermatogenesis - meiosis completed continuously; Oogenesis - Meiosis I at ovulation, Meiosis II upon fertilization.
    • Resource Allocation: Sperm - small, few resources; Egg - large, nutrient-rich.

    Chromosomal Material in Meiosis Phases

    • Prophase I has the most chromosomal material.

    Restoration of Diploid Number

    • Diploid number is restored through fertilization.

    Cancer Cells

    • Cancer cells divide uncontrollably without regulation.
    • Lack normal cell functions, communication, and may detach from tissues easier.
    • Secrete growth hormones and attract blood vessels to provide nutrients.
    • Risk factors include genetic predisposition, exposure to toxins, radiation, and UV light.
    • Uncontrolled growth leads to tumor formation.
    • Treatments: Radiation and chemotherapy to target dividing cells.

    Gametogenesis

    • Involves production of gametes through meiosis.

    Stem Cells

    • Undifferentiated cells with the potential to become specialized cells.
    • Somatic stem cells are found throughout the body.
    • Totipotent: Can give rise to all cell types, including the placenta.
    • Pluripotent: Can give rise to all cell types except the placenta.
    • Multipotent: Can give rise to a limited number of cell types.

    Cell Differentiation

    • Stem cells activate specific parts of their DNA to become specialized cells.
    • Transcription factors play a crucial role in gene expression, determining the type of cell that forms.
    • Internal cues (e.g., transcription factors in the cytoplasm of the zygote) and external cues (e.g., signaling from other cells or environmental factors) influence cell differentiation.

    Cell Aging

    • Cellular processes decline over time due to accumulation of damage or loss of repair mechanisms.
    • Can contribute to a reduced ability to function and increased susceptibility to disease.

    Cell Death

    • Cell death occurs through apoptosis (programmed cell death) or necrosis (cell death due to injury).
    • Apoptosis:
      • Intrinsic pathway is triggered by internal cell damage.
      • Extrinsic pathway is triggered by external signals.
      • Involves a series of steps: Initiation, signal transduction, activation of caspases, execution phase, formation of apoptotic bodies, and phagocytosis.
    • Necrosis:
      • Caused by injury, infection, toxins, or loss of blood supply.
      • Involves loss of membrane integrity, organelle swelling, enzyme release, and cell breakdown.

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    Description

    This quiz covers the key stages of the cell cycle, including interphase and mitosis, along with their checkpoints and special phases like G0. Understand how cells grow, replicate DNA, and ensure proper division through various stages and checkpoints.

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