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Medicine LibreTexts

2: Cytology

  • Page ID
    12522
  • In this lab students will learn to identify main external and internal cell structures. Use your textbook to identify and label the cell structures listed below. Watch the Cytology Lab Video associated with this lab. http://www.screencast.com/t/zDcEGmYAi2F

    LAB 2 EXERCISE 2-1

    Structure of a Representative Cell: Please identify and label the following cell structures listed below. Place the appropriate letter(s) on the line between the numbers and the name.

    1. Plasma membrane 7. Golgi complex

    2. Cytosol (described in text) 8. Golgi vesicles

    3. Nucleus 9. Mitochondria

    4. Nuclear envelope 10. Lysosome

    5. Rough endoplasmic reticulum 11. Centriole

    6. Smooth endoplasmic reticulum

    F

    H

    I

    D

    E

    G

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    C

    B

    J

    A

    K

    LAB 2 EXERCISE 2-2

    The Cell Interior

    Please identify and label the following cell structures listed below. Watch the Cytology Lab Video as requested before 2.1 to help you complete this activity. Place the appropriate letter(s) on the line between the numbers and the name. “NA” = not applicable, do not use.

    1. Plasma membrane 6. Golgi complex

    2. Nucleus 7. Golgi vesicles

    3. Nuclear envelope 8. Mitochondria

    4. Rough endoplasmic reticulum 9. Lysosome

    5. Smooth endoplasmic reticulum 10. Centriole

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      C

      *There may be multiple pictures of the same structure

      A

      B

      D

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      E

      AB

      AC

      AD

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      AD

      NA

      AE

      NA

      BC

      Mitosis In A Whitefish Embryo

      Introduction: The Cell Cycle and Mitosis:

      The cell cycle refers to a series of events that describe the metabolic processes of growth and replication of cells. The bulk of the cell cycle is spent in the “living phase”, known as interphase. Interphase is further broken down in to 3 distinct phases: G1 (Gap 1), S (Synthesis) and G2 (Gap 2). G1 is the phase of growth when the cell is accumulating resources to live and grow. After attaining a certain size and having amassed enough raw materials, a checkpoint is reached where the cell uses biochemical markers to decide if the next phase should be entered. If the cell is in an environment with enough nutrients in the environment, enough space and having reached the appropriate size, the cell will enter the S phase. S phase is when metabolism is shifted towards the replication (or synthesis) of the genetic material. During S phase, the amount of DNA in the nucleus is doubled and copied exactly in preparation to divide. The chromosomes at the end of G1 consist of a single chromatid. At the end of S phase, each chromosome consists of two identical sister chromatids joined at the centromere.

      When the DNA synthesis is complete, the cell continues on to the second growth phase called G2. Another checkpoint takes place at the end of G2 to ensure the fidelity of the replicated DNA and to re- establish the success of the cell’s capacity to divide in the environment. If conditions are favorable, the cell continues on to mitosis.

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      Left: Eukaryotic cell cycle is governed by expression of cyclin proteins along with their activity. Credit: Jeremy Seto (CC-BY-SA)

      Mammalian cells in culture going through the Cell Cycle. Green marker proteins expressed during the G1 phase. Red marker proteins are expressed during S/G2/M.

      During the G1 to S transition, fluorescence disappears as the marker proteins also transition in expression.

      https://youtu.be/nlMVeW594F4

      Follow this link above to view a mitosis video.

      Mitosis is the process of nuclear division used in conjunction with cytokinesis to produce 2 identical daughter cells. Cytokinesis is the actual separation of these two cells enclosed in their own cellular membranes. Unicellular organisms utilize this process of division in order to reproduce asexually.

      Prokaryotic organisms lack a nucleus, therefore they undergo a different process called binary fission. Multicellular eukaryotes undergo mitosis for repairing tissue and for growth. The process of mitosis is only a short period of the lifespan of cells. Mitosis is traditionally divided into four stages: prophase, metaphase, anaphase and telophase.

      The actual events of mitosis are not discreet but occur in a continuous sequence—separation of mitosis into four stages is merely convenient for our discussion and organization. During these stages important cellular structures are synthesized and perform the mechanics of mitosis. For example, in animal cells two microtubule organizing centers called centrioles replicate. The pairs of centrioles move apart and form an axis of proteinaceous microtubules between them called spindle fibers.

      These spindle fibers act as motors that pull at the centromeres of chromosomes and separate the sister chromatids into newly recognized chromosomes. The spindles also push against each other to stretch the cell in preparation of forming two new nuclei and separate cells. In animal cells, a contractile ring of actin fibers cinch together around the midline of the cell to coordinate cytokinesis. This cinching of the cell membrane creates a structure called the cleavage furrow.

      Eventually, the cinching of the membrane completely separates into two daughter cells. Plant cells require the production of new cell wall material between daughter cells. Instead of a cleavage furrow, the two cells are separated by a series of vesicles derived from the Golgi. These vesicles fuse together along the midline and simultaneously secrete cellulose into the space between the two cells. This series of vesicles is called the cell plate.

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      LAB 2 EXERCISE 2-3

      1. Obtain a slide of a whitefish embryo (blastula) from the slide box at your table.

      2. Follow the checklist above to set up your slide for viewing.

      3. View the slide on the objective which provides the best view. Find the representative object.

      4. In the circles below the name, draw a representative sample of the stage of mitosis, taking care to correctly and clearly draw the true shape in the slide. Draw your structures proportionately to their size in your microscope’s field of view.

      5. Fill in the blanks next to your drawing.

      6. Repeat this for each of the mitosis phases seen below.

    A) Prophase

    image

    Function of this phase:

    B) Metaphase

    Function of this phase:

    C) Anaphase

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    Function of this phase:

    D) Telophase/cytokinesis

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    Function of this phase:

    When storing a microscope you should always follow this list:

    1. Remove any slide found on the stage and return it to the slide box.

    2. Rotate the smallest lens or no lens into place above the stage. Lower the stage a few turns.

    3. Loosely coil the cord in your hand starting near the microscope and working toward the plug.

    4. Hang the coiled cord over one ocular lens.

    5. Look at the number on the back of the microscope, return that scope to its numbered box.

    6. If there’s already a microscope in that numbered box, check its number and move it. If it is not numbered simply push it to the back of the box and place yours closer to the front. We have a few extra microscopes which we store in this fashion.

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