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Questions and Answers

What is the primary function of the condenser in a microscope?

  • To magnify the image of the specimen.
  • To create a virtual image of the specimen.
  • To regulate the amount of light entering the microscope.
  • To concentrate light onto the specimen. (correct)

    • Which component of the microscope is responsible for creating a real, intermediate image of the specimen?

  • The eyepiece.
  • The condenser.
  • The lens. (correct)
  • The light source.

    • What is the typical magnification range for dry lenses in a microscope?

  • 10 to 30 times.
  • 200 to 300 times.
  • Up to 60 times. (correct)
  • 90 to 150 times.

    • What substance is typically used with immersion lenses to enhance resolution?

    <p>Immersion oil.</p> Signup and view all the answers

    What is a key difference between the image produced by standard optical microscope and the real object?

    <p>The image is a virtual and magnified representation of the object.</p> Signup and view all the answers

    Which of the following best describes the role of a diaphragm in a microscope's optical system?

    <p>To regulate the amount of light entering the condenser.</p> Signup and view all the answers

    What is the main purpose of the mechanical system of a microscope?

    <p>To ensure the proper positioning of the optical elements.</p> Signup and view all the answers

    What is the resolution improvement that can be achieved with immersion oil?

    <p>Up to 0.16 µm.</p> Signup and view all the answers

    What is the primary purpose of using immersion oil in microscopy?

    <p>To prevent the scattering of light rays as they leave the coverslip.</p> Signup and view all the answers

    The magnification of a microscope is determined by:

    <p>The product of the objective lens and eyepiece magnifications.</p> Signup and view all the answers

    What does the resolving power of a microscope refer to?

    <p>The minimum distance at which two objects can be seen separately.</p> Signup and view all the answers

    Which component of a microscope is used to change the magnification by switching different objective lenses?

    <p>The nose piece (revolver).</p> Signup and view all the answers

    What is the function of the mechanical stage on a microscope?

    <p>To hold the slide and allow horizontal movement.</p> Signup and view all the answers

    Which part of the microscope is primarily used for initial focusing using large adjustments?

    <p>The coarse adjustment knob.</p> Signup and view all the answers

    Where is the virtual image of the specimen formed?

    <p>Inside the head or tube between the lenses.</p> Signup and view all the answers

    If a microscope has an objective lens with $40x$ magnification and an eyepiece with $10x$ magnification, what is the total magnification?

    <p>$400$ times</p> Signup and view all the answers

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

    <p>Doubling of the DNA content within each chromatid.</p> Signup and view all the answers

    Which of the following best describes the state of chromosomes during interphase?

    <p>Non-condensed and not visible as separate entities under a microscope.</p> Signup and view all the answers

    What is the role of the G1 phase in the cell cycle?

    <p>Preparation of the cell for DNA replication.</p> Signup and view all the answers

    During which phase of the cell cycle does the DNA content of the cell double?

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

    What is the key event that occurs during the G2 phase of the cell cycle?

    <p>Synthesis of mitotic apparatus components and chromosome condensation.</p> Signup and view all the answers

    What is the M phase in the cell cycle also known as?

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

    Which of the following best describes the G0 phase?

    <p>A resting phase where cells do not divide but maintain metabolic functions.</p> Signup and view all the answers

    Which of these is NOT a task of the cell cycle?

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

    What can cause a cell to enter the G0 phase?

    <p>The beginning of cell differentiation process.</p> Signup and view all the answers

    What is a cell cycle control system primarily responsible for?

    <p>Ensuring key processes of the cycle happen in the correct order.</p> Signup and view all the answers

    What is the outcome of mitosis in terms of chromosome number?

    <p>The daughter nuclei have the same number of chromosomes as the parent nucleus.</p> Signup and view all the answers

    What are the G1 and G2 phases often called?

    <p>Stagnation phases</p> Signup and view all the answers

    What are the two main processes that constitute the M phase?

    <p>Karyokinesis (mitosis) and cytokinesis.</p> Signup and view all the answers

    During which phase of the cell cycle does the most intensive metabolic activity take place?

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

    What occurs during cytokinesis?

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

    During which phase of mitosis do sister chromatids separate?

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

    What event marks the beginning of prometaphase?

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

    In which phase are chromosomes aligned in the equatorial plane of the spindle?

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

    What structure is responsible for dividing the cell into two daughter cells?

    <p>Contractile ring</p> Signup and view all the answers

    During which stage does the nuclear envelope reassemble around each set of chromosomes?

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

    What structure attaches chromosomes to the spindle microtubules?

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

    What event leads to the formation of daughter chromosomes?

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

    Which phase is characterized by the movement of centrosomes away from each other?

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

    What is the primary purpose of using immersion oil in microscopy, as implied by the provided images?

    <p>To increase the resolution and clarity of the image.</p> Signup and view all the answers

    In the context of the exercise, what type of cells are being observed during mitosis?

    <p>Apical meristem cells of the onion root.</p> Signup and view all the answers

    Which phase of mitosis is characterized by the alignment of chromosomes at the cell's equator?

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

    During which phase of mitosis do sister chromatids separate and move towards opposite poles of the cell?

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

    What is the final stage of mitosis, where the nuclear envelope reforms and the chromosomes decondense?

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

    In the context of cell division, what is a chromatid?

    <p>One of two identical strands of a replicated chromosome.</p> Signup and view all the answers

    If a cell has 3 pairs of chromosomes, and each chromosome has been doubled, what structure would you visualize at metaphase, prior to separation?

    <p>6 chromosomes, each with a sister chromatid.</p> Signup and view all the answers

    What key process is crucial for the separation of chromatids during anaphase?

    <p>Action of the spindle fibers.</p> Signup and view all the answers

    If a cell with 10 picograms of DNA in the G1 phase completes the S phase, how much DNA, in picograms, would be present during the G2 phase?

    <p>20</p> Signup and view all the answers

    What would be the immediate consequence if a cell failed to complete the S phase before entering mitosis?

    <p>The cell would be unable to properly segregate chromosomes at anaphase and the daughter cells would be aneuploid.</p> Signup and view all the answers

    In a cell progressing through the cell cycle, during which stage would you expect to observe the highest level of gene expression?

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

    A treatment that inhibits chromosome condensation would directly affect which process or phase of the cell cycle?

    <p>Initiation of the M phase</p> Signup and view all the answers

    Considering the role of the cell cycle control system, what would be the MOST immediate consequence if this system failed in a cell?

    <p>The cell would undergo uncontrolled and dysregulated cell division.</p> Signup and view all the answers

    If a cell has undergone one cell cycle, starting with a single cell in the G1 phase, how many genetically identical cells would exist after mitosis and cytokinesis?

    <p>2</p> Signup and view all the answers

    In rapidly dividing cells, which part of the cell cycle tends to be the shortest, reflecting minimal preparation time for the proceeding division?

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

    Which of the following correctly explains the impact of the S phase on the state of the chromosome?

    <p>Each chromosome duplicates resulting in two identical sister chromatids.</p> Signup and view all the answers

    If a cell with a 2n DNA content completes the S phase without any errors, what would be its immediate DNA content?

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

    A cell in the G0 phase has which characteristic?

    <p>It maintains standard metabolic functions without cell division.</p> Signup and view all the answers

    What is the direct consequence of successful mitosis in a diploid cell?

    <p>Two diploid cells</p> Signup and view all the answers

    Which of the following describes the primary purpose of the 'checkpoints' observed in the G1 and G2 phases?

    <p>To ensure the cell has resources for the following phases before moving forward.</p> Signup and view all the answers

    If a cell is observed to have condensed chromosomes and is actively synthesizing the proteins needed for the mitotic spindle, then which phase of the cell cycle is it MOST likely in?

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

    What cellular change directly results from the synthesis taking place in the S phase?

    <p>An increase from a 2n to a 4n DNA content</p> Signup and view all the answers

    Which stage of the cell cycle is immediately followed by mitosis?

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

    How does the metabolic activity in the G0 phase compare to the other phases of the cell cycle?

    <p>It remains stable and supports normal cell functions.</p> Signup and view all the answers

    What is the primary reason for using immersion oil with certain microscope objective lenses?

    <p>To prevent light scattering by reducing refraction and improving the resolving power.</p> Signup and view all the answers

    If a microscope has a $20x$ objective lens and a $10x$ eyepiece, and you then change to a $40x$ objective lens, what is the increase in total magnification?

    <p>$200x$</p> Signup and view all the answers

    Which component of the microscope is responsible for adjusting the vertical position of the condenser?

    <p>The mechanical system of the condenser.</p> Signup and view all the answers

    What does the resolving power of a microscope directly determine?

    <p>The ability to distinguish between two closely positioned objects.</p> Signup and view all the answers

    In microscopy, what is the specific function of the fine adjustment knob?

    <p>To precisely focus on the specimen after coarse adjustments are made.</p> Signup and view all the answers

    What function does the nose piece (revolver) of a microscope serve?

    <p>It is a rotating disc containing multiple objective lenses allowing for quick changes.</p> Signup and view all the answers

    What is the role of the mechanical stage in microscopy?

    <p>To move the specimen horizontally across the field of view on the X and Y axes.</p> Signup and view all the answers

    What is the relationship between the magnification of a microscope’s objective lens, eyepiece and the total magnification?

    <p>The total magnification is the product of the objective and eyepiece magnification.</p> Signup and view all the answers

    If a cell failed to properly form a mitotic spindle, which phase of mitosis would be most directly affected?

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

    If a drug prevented the shortening of kinetochore microtubules, which of the following would most directly be inhibited?

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

    What would be the immediate consequence if a cell could not properly assemble the contractile ring?

    <p>Failure of the cell to form two distinct daughter cells</p> Signup and view all the answers

    During which phase of mitosis do the kinetochores of sister chromatids exhibit attachment to spindle microtubules originating from opposite poles?

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

    If a cell had a mutation that prevented the synchronised separation of sister chromatids, what would be the most direct consequence?

    <p>The formation of daughter cells with incorrect chromosome numbers</p> Signup and view all the answers

    At what stage of mitosis would you typically expect to observe distinct daughter chromosomes, each moving towards opposite poles of the cell?

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

    If a cell completed mitosis but failed to undergo cytokinesis, what would be a direct consequence?

    <p>The formation of two nuclei within a single cell</p> Signup and view all the answers

    In the context of the cell cycle, what would be the result if a cell could not reassemble its nuclear envelope after mitosis?

    <p>The chromosome would remain unconfined in the nucleus/cytoplasm</p> Signup and view all the answers

    Based on the provided exercise instructions, which of the following represents the correct sequence of steps when observing mitotic division in onion root tip cells?

    <p>Prepare the slide, focus under 4x lens, apply oil immersion, draw the phases</p> Signup and view all the answers

    In exercise 4, when drawing the phases of mitosis for 3 pairs of chromosomes, which step is crucial to visualise chromosomes with both single and double chromatids?

    <p>Drawing all phases from prophase to telophase</p> Signup and view all the answers

    Referring to Exercise 5, if a cell moves past stage 4, which stage in mitosis is the next most likely to be observed?

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

    If a student is asked to draw mitosis of 3 pairs of chromosomes, what is the minimum number of chromatids that a cell must have at the start of metaphase?

    <p>12</p> Signup and view all the answers

    Considering the provided material, what is the primary goal of including drawings of mitosis phases in an exercise?

    <p>To enhance the student's understanding of chromosome behavior during different stages.</p> Signup and view all the answers

    Based on the exercise protocols, when comparing observations using the 4x objective and oil immersion, what are students expected to note?

    <p>The image is larger using oil immersion and has a higher resolution.</p> Signup and view all the answers

    In Exercise 5, the numbers 1-8 likely refer to different stages in cellular processes. What concept about cell division would be the goal for the full list of numbers to express?

    <p>The different phases of mitosis and cytokinesis.</p> Signup and view all the answers

    If a student visualizes onion root tip cells during anaphase with 3 pairs of chromosomes, and then a second cell during with two pairs of chromosomes, how many total single chromatids would be seen moving towards each pole in cell 1 compared to cell 2?

    <p>6, then 4</p> Signup and view all the answers

    An optical microscope's light path is adjusted to enhance resolution; which action is MOST critical when transitioning from a low-power to a high-power objective lens?

    <p>Increasing the light intensity and potentially utilizing immersion oil with the appropriate objective.</p> Signup and view all the answers

    If a microscope's optical system is solely composed of an objective lens with a magnification of 75x and an eyepiece with a magnification of 20x and no immersion oil is used. By which factor can the image be magnified?

    <p>By a maximum of 1500x magnification with a limit to the resolving power set by the air gap</p> Signup and view all the answers

    When viewing a prepared slide using immersion microscopy, why MUST the immersion oil bridge be formed between both the lens and the coverslip in the preparation?

    <p>To minimize light scattering, thereby maximizing resolution by directing light through a more homogeneous medium</p> Signup and view all the answers

    A student is observing a cell in metaphase using a microscope. Which setup demonstrates the MOST appropriate use of a microscope's optical components?

    <p>Sharp, intense illumination, partially closed diaphragm, using high power objective with immersion oil</p> Signup and view all the answers

    If an error occurs such that chromatid separation is prevented during mitosis. Which of these options below best describes the immediate consequence following cell division?

    <p>Two daughter cells will each have double the normal genetic material.</p> Signup and view all the answers

    During the preparation of a slide for microscopic observation, the cover glass was inadvertently omitted. This is most likely to impact?

    <p>The ability to achieve optimal focus using immersion oil</p> Signup and view all the answers

    While observing mitosis, a student notices that the centrosomes have moved to opposite poles of a cell but the chromosomes remain uncondensed. Based on the phases of mitosis, this observation is MOST consistent with which stage?

    <p>Early interphase.</p> Signup and view all the answers

    A slide preparation is made using cells taken from the onion root tip. Some of the cells on the slide appear flattened by pressure. Which of following statements is a correct interpretation of the cell morphology seen in this slide?

    <p>These cells are likely in metaphase, due to the compression applied</p> Signup and view all the answers

    Study Notes

    Optical Microscope Construction

    • Microscopes combine optical and mechanical systems
    • Optical system has lighting and magnification components
    • First part illuminates the specimen
    • Second part creates the magnified image of the specimen
    • Mechanical system positions optical components
    • Image is magnified and virtual
    • Microscopes are basic devices in biological labs

    Optical Microscope Components

    • Light Source: Built-in light bulb with reflector; adjusts light intensity based on magnification
    • Condenser: Set of lenses to concentrate and focus light onto the specimen
    • Diaphragm: Regulates light entering the condenser
    • Lenses: Magnify the image; dry lenses magnify up to 60x, immersion lenses 90-150x
    • Immersion Lens: Uses a liquid (oil) between the lens and specimen to improve resolution (labeled OIL or IMMERSION OIL)
    • Ocular Lens (Eyepiece): Creates a virtual image of the specimen; magnification varies (2x-30x)

    Mechanical Microscope Components

    • Base and Arm: Provide structural support
    • Mechanical Stage: Holds specimen and moves it horizontally
    • Coarse Adjustment: Moves stage to focus image
    • Fine Adjustment: Precisely adjusts focus
    • Nose Piece: Holds and rotates objective lenses
    • Head (Tube): Space between lens and eyepiece where the image is formed
    • Condenser Adjustment: Vertically adjusts the condenser position

    Cell Cycle

    • Interphase: Cell growth and metabolic activity before mitosis; longest phase except for rapidly dividing cells
    • Gap 1 (G1) Phase: Pre-DNA synthesis, cell growth and organelle duplication
    • Synthesis (S) Phase: DNA replication occurs (doubling the DNA content)
    • Gap 2 (G2) Phase: Pre-division phase, cell organelles and components for cell division are synthesized
    • M Phase (Mitosis): Nucleus divides through several stages
    • Prophase: Chromatin condenses into chromosomes; nuclear envelope breaks down; mitotic spindle forms -Chromosomes condense -Nuclear envelope breaks down -Mitotic spindle forms
    • Prometaphase: Spindle fibers attach to chromosomes -Spindle fibers attach to chromosomes
    • Metaphase: Chromosomes align at the metaphase plate -Chromosomes align at metaphase plate
    • Anaphase: Sister chromatids separate and move to opposite poles -Sister chromatids separate and move to opposite poles
    • Telophase: Chromosomes reach poles; nuclear envelope reforms; cytokinesis begins -Chromosomes reach poles -Nuclear envelope reforms -Cytokinesis begins
    • Cytokinesis: Cytoplasmic division; two daughter cells are formed -Cytoplasmic division; two daughter cells are formed

    Mitosis

    • Mitosis (karyokinesis) is the division of the cell nucleus
    • M Phase involves mitosis and cytokinesis
    • Mitosis phases include prophase, prometaphase, metaphase, anaphase, and telophase.

    Practical Exercises

    • Exercise 1: Describe the microscope parts and their functions
    • Exercise 2: Observe a specimen at different magnifications and draw the image, using immersion oil; Focus on a specific area, draw detail
    • Exercise 3: Find and draw onion root tip cells in different mitotic phases (prophase, metaphase, anaphase, telophase)
    • Exercise 4: Draw 3 pairs of chromosomes in mitotic phases, showing double/single chromatids
    • Exercise 5: Identify the phase of cell division in provided images

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    Related Documents

    Exercise No. 2: Microscopic Observations of Mitotic Divisions - PDF

    Description

    Test your knowledge on the essential components and functions of a microscope. This quiz covers topics such as magnification, resolution, and the role of various parts in the optical system. Perfect for students studying biology or those in the field of microscopy.

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