Mitosis

Mitosis Revision Cards

Based on pages 30-31 in OCR Biology Textbook. May be useful for other exams boards aswell.

Please take a look and comment/rate, it will be much appreciated.

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  • Created by: JessicaB
  • Created on: 03-01-12 22:38

Intro.

Key Definition:

Mitosis refers to the process of nuclear division where two gentically identical nucei are formed from one parent cell nucleus.

Remember!!- During mitosis, two nuclei are formed. Not two complete cells. Mitosis is just a stage in the complete cell cycle.

Cell Cycle:

1. Interphase-DNA Replication

2. Mitosis-Nucleus divides

3. Cytokinesis-Cytoplasm cleaves

4. Growth phase




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Pretty useful diagram...

(http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/47739/sadava_9_3_big.gif)

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Importance of producing new cells

Past Exam Question

State 3 reasons why mitosis is important to organisms (OCR Jan 2009)

There is 4 answers which are accepted. Any 3 of them will get you full marks.

1. Growth of tissue/organisms

2. Replace cells/Repair tissue

3. Asexual reproduction

4. Maintain chromosome number in all cells

Please note: It is growth of tissue and repair of tissue NOT CELLS

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Stages of Mitosis

There are 4 stages of mitosis-prophase, metaphase, anaphase and telophase.

OCR give you the mnemonic PMAT to help you remember the stages. To be honest, i don't think it's very memorable. That's why i prefer...

Put My Answer There

Pehaps Men Are Toads(http://www.ict4us.com/mnemonics/images/de_zellteilungsstadien.gif)

ProMote Another Tadpole

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Prophase

  • Chromosomes shorten and thicken (supercoil). Therefore can be seen.
  • Nuclear envelope breaks down and disappears.
  • Centriole divide into two and each daughter centriole moves to opposite poles of the cell to(http://www.huber-erstehilfe.de/RettAss/Die_Zelle/Zellteilung/ZellteilungProphase.jpg) form spindle.

                             Spindle Fibre     

Supercoiled Chromosome

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Metaphase

  • Chromosomes move to central region of the spindle
  • Each becomes attached to a spindle thread by its centromere.(http://upload.wikimedia.org/wikipedia/commons/e/ee/Metaphase.png)
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Anaphase

  • Sister chromatids separate when centromere splits
  • Spindle fibres shorten, pulling chromatids from each other towards poles
  • They assume a V-shamebecause the centromeres lead.(http://www.phschool.com/science/biology_place/labbench/lab3/images/anaphase.gif)
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Telophase

  • New nuclear envelope forms around each set of chromosomes
  • Spindle breaks down and disappears
  • Chromosomes uncoil so they are no longer visible under a light microscop(http://www.edupic.net/Images/Mitosis/telophase.png)e
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Cytokinesis

After mitosis, cytokinesis begins. The whole cells splits into two cells when the cell surface membrane cleaves. Each cell contains the same set of chromosomes/DNA and are therefore identical. (http://www.glogster.com/media/5/20/71/10/20711076.gif)

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How i remember what happens in each stages.

Ok, so this is how i remember. It's kind of weird but it works for me so maybe it works for you or maybe not...

Prophase- Ok well Pro usually means that it's the first. Because it is the first stage which we already know from the mnemonics on the other card. Therefore i just think that the chromosomes must be visible in order to see the following stages. Sorry, that ones tricky to relate to.

Metaphase- M is for middle. The chromosomes line up in the middle of the cell.

Anaphase- A is similar to the V-shape the chromatids make when being pulled away from each other. (if the V was the other way round)

Telophase- Ok, this ones weird. I remember this as like a telephone. You have the speaker which you hear out and the microphone you speak into. These two parts of the telephone can represent the two nuclei formed by mitosis.

Thankyou for reading, hope it helps! :)

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