Lesson 3.5.3

3.5.3 page 2


Read

In previous lessons you have learned how our cells follow a cycle. From origin through G1, S, and G2 of Interphase, the cell grows, divides its DNA, then gets ready for cell division. If you need to refresh your understanding of this process, take a moment to review the following animation.

 

Mitosis is an orderly process that carefully divides a cell’s chromosomes. These chromosomes were copied precisely in S Phase so that each one has the identical genetic content. When Mitosis is complete, cytokinesis divides the cell physically into two identical daughter cells, which are exact replicas of the parent cell. Consider the summary on p. 557 in your text. You may wish to summarize this information for your course folder. Study both the computer graphic and the actual slides of each phase.

 

Mitosis is a process, and is actually more of a continuum than a set of snap shots. However, for study purposes, it can be divided into four distinct phases. Prophase, Metaphase, Anaphase, and Telophase. These phases are very important, and if you can come up with an easy mnemonic for PMAT it would be a great study and memorization tool! Your can read more about these phases on pages 557 and 558 of your textbook.

 

Watch and Listen

You should now have functional knowledge of each of the phases of mitosis. Review how they work together by watching the following video. 

 

Going Beyond

You could be creative too. Why not come up with your own poem or song about mitosis and share it with your classmates? Be sure to let your instructor know that you would like to complete this activity, and once you have finished, save your work to your course folder.

 

Read

Consider the two sets of slide images below. How are they similar? How are they different?

Microscope slide showing several root tip cells undergoing mitosis.
Microscope slide showing several white fish cells undergoing mitosis.



If you have good observation skills you should notice two clear differences between plant and animal mitosis. Firstly, plant cell walls are rigid and cannot go through cleavage. Instead, a new cell wall is formed between the daughter cells called a cell plate. Secondly, plant cells do not have centrioles. They do form a spindle apparatus to move chromosomes around, but must anchor this apparatus to the cell wall instead of to the centrioles as animal cells do.

 

Labs

 Use the Exploration Guide to learn how to use the Cell Division Exploration activity needed to complete the assignment.

Complete the online Cell Division Exploration.

(Put your username and password into the top login box.)

Make sure you allow the simulation to run for around 100 simulation hours or more to obtain the best results.

 

Self-Check

Here is a chance to check your understanding. Complete the following questions on Mitosis and cellular division, and then check your answers. If any of these questions give you trouble, ask your instructor for clarification about that concept.

  1. Label the following terms on the flow chart below: mother cell, daughter cells, chromosomes, S phase, metaphase, separation of chromatids, prophase.

    Flow chart of mitosis with blanks to fill in.
  2. A skin cell taken from a chimpanzee contains forty-eight chromosomes.

    1. How many chromosomes would there be in the nerve or bone cells of this animal?
    2. If a skin cell of the chimpanzee underwent cell division, how many chromosomes would there be in each daughter cell?
  3. What role do centrioles play in cell division of animal cells?
  4. Match the event described in each statement with the correct stage of mitosis labeled on the diagram.

    A. Interphase

    B. Prophase

    C. Metaphase

    D. Anaphase

    E. Telephase

    Diagram

    Event

    ________ a.

    Normal growth and functioning of the cell occurs here.

    ________ b.

    Chromosomes replicate to produce two sets of chromosomes in preparation for cell division.

    ________ c.

    Chromosomes with their duplicates still attached shorten by
    coiling, thus becoming visible under the microscope.

    ________ d.

    Centrioles migrate to opposite sides of the cell and the
    nuclear membrane dissolves.

    ________ e.

    Spindle fibres grow from each centriole and attach to the centromere of each chromatid pair.

    ________ f.

    Chromatid pairs still joined at the centromere line up along the middle of the cell, called the metaphase plate.

    ________ g.

    Chromatids are pulled apart by shortening of the spindle fibres. One complete set of chromosomes is pulled to each pole.

    ________ h.

    Chromosomes uncoil, spindle fibres dissolve, and cytoplasm divides. Two daughter cells are formed.
  5. Name the process of cytoplasmic division and describe how it is different in plant and animal cells.
Check your work.
Self-Check Answers
  1. a) mother cell, b) S phase, c) prophase, d) metaphase, e) separation of chromatids or anaphase, f) daughter cells

    1. There would be forty-eight chromosomes in nerve and bone cells.
    2. There would be forty-eight chromosomes in each daughter cell.
  2. Centrioles provide attachment for spindle fibres and form the points to which chromatids are pulled during anaphase.

    1. A
    2. A
    3. B
    4. B
    5. B
    6. C
    7. D
    8. E
  3. Division of the cytoplasm is called cytokinesis. In animal cells the cytoplasm pinches off, separating the two daughter cells. In plant cells, a new cell wall must form between the two nuclei because the existing cell walls are rigid and do not allow for pinching. The new cell wall is called a cell plate.