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KS4 Biology

KS4 Biology. Cell Division and Fertilization. Contents. Cell Division and Fertilization. Introducing cell division. What is mitosis?. How many cells?. An adult human is made up of about 100 trillion cells. That’s 100 000 000 000 000 cells!.

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KS4 Biology

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  1. KS4 Biology Cell Division and Fertilization

  2. Contents Cell Division and Fertilization Introducing cell division What is mitosis?

  3. How many cells? An adult human is made up of about 100 trillion cells. That’s 100 000 000 000 000 cells! Everyone started out as just one single cell. How does one cell become 100 trillion?

  4. By cell division – called…..MITOSIS This animation will be explained in more detail in the slides to come. For now, just sit back and watch it.

  5. Mitosis Why is mitosis important? For growth – How else would you go from being a single fertilized egg cell to the young person you are today?

  6. To replace worn/ damaged cells – - did you know that we shed our skin cells about every 35 days. But don't worry, we do not shed all our skin cells at the same time like snakes do. In human beings, only the skin cells that are old are shed, others are not.

  7. To repair damaged tissue -when you cut yourself, new skin cells will grow to seal the wound. These new cells come from preexisting cells found near the wound that divided many, many times.

  8. Cell division and genetic information Cells don’t just split in half when they divide. If they did, there wouldn’t be much of the cells left! It is essential that the genetic information carried in a cell is transferred to the new cells. Where is genetic information carried in a cell? When a cell divides, how can this genetic information be transferred without any of it being lost?

  9. Cell division and chromosomes Chromosomes in the nucleus carry the genetic information of a cell. Chromosomes must be accurately copied and passed on during cell division. This is important to make sure that no genetic information is lost.

  10. Mitosis begins with a single cell. How many chromosomes does this cell contain? (answer: 4) First the cell makes a copy of each chromosome… What is mitosis? original cell …then it divides. cell division Each new cell has a full set of chromosomes and is identical to the original cell. 2 new cells

  11. What is mitosis? Each new cell can keep on dividing by mitosis. Mitosis makes new cells for growth and repair in all living things. That’s how you get from one cell to 50 billion!

  12. Stages of Mitosis At the end of Interphase, a cell that is ready to divide looks like this: Loosely coiled DNA The cell has grown to nearly 2X its original size, and the DNA has been copied.

  13. The actual process of dividing is called : Mitosis There are 4 main stages: Prophase Metaphase Anaphase Telophase

  14. Prophase Prophase • nuclear membrane starts to break down • The loosely coiled DNA condenses (gets supercoiled)- forms chromosomes. You can see chromosomes (like the letter “X”) in a microscope • Centrioles release spindle fibres; spindle fibers will attach to the centromere of each chromosome • by the end of prophase, the nuclear membrane is completely gone

  15. Metaphase • The chromosomes move to the middle of the cell • spindle fibers, attached to the centromere of each chromosome, help the chromosomes move to the middle

  16. Anaphase • Each chromosome separates so that a copy of each DNA molecule moves to the poles of the cell • Spindle fibers pull the separated chromosomes to the poles (ends) of the cell

  17. Telophase • The spindle fibers disappear • A nuclear membrane reforms around each set of chromosomes • The chromosomes begin to uncoil (from supercoiled to loosely coiled) • The cell begins to pinch apart at the centre until it completely separates into 2 distinct cells, each with its own set of genetic material (DNA). This division of the cytoplasm is called cytokinesis. Cell organelles are also equally distributed between the daughter cells

  18. On the next slide is an animation of mitosis. In your kit is a step by step narrative of what you will see. Read the script as you play the animation. Repeat the process in order to get a better understanding.

  19. Mitosis animation

  20. Mitosis summary How does mitosis turn one cell into two new cells?

  21. Stages of mitosis activity Wwha Wwhh Whad

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