© boardworks ltd 2004 1 of 29 get notebooks 4 minutes for mission countdown use notes if needed

© Boardworks Ltd 20041 of 29

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Biology

Cell Division and Fertilization


5 minutes to write your Journal Entry

*participation grade*

Why do we need to replace cells? When has

your body ever needed to replace cells? How do you think this happens?

Show me your paragraph when you are finished


Telophase

Prophase

Metaphase

Anaphase

Interphase


Facts

• 30,000 -40,000 skin cells die every hour

• In 1 day you lose a million skin cells

• The dust in your house….made mostly of dead skin cells

• In 1 year, you lose 8 pounds of skin cells


• Some white blood cells only live a few hours

• Red blood cells have a life span of 120 days

• Nerve/brain cells live as long as you do…which why its important you don’t kill them(example: with drugs) because they don’t come back!


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?


Mitosis – Cell Division

This animation will be explained in more detail in the slides to come. For now, just sit back and watch it.


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?


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.


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.


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 informationcarried in a cell?

When a cell divides, how can this genetic information be transferred without any of it being lost?


Cell division and chromosomes

Chromosomes (parts of DNA) in the nucleus carry the genetic info

Chromosomes must be accurately copied and passed on during cell division.

This is important to make sure that no genetic information is lost.


What is mitosis?

new cell has full set of chromosomes and is identical to the original cell.

Mitosis begins with 1 cell. How many chromosomes does this cell contain?(answer: 4)

First the cell makes a copy of each chromosome…

original cell

cell division

2 new cells

…then it divides.


What is mitosis?

Each new cell can keep on dividing by mitosis.

Mitosis makes new cells by dividing them for growth and repair in all living things. That’s how you get from one cell to 50 billion!


So what is the life cycle of a cell?

Think about humans, can humans reproduce at birth? What has to happen first?

Lets watch an animation that shows the cell cycle


Mitosis animation


In foldable: write definition and detailed picture under flap

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.


The actual process of dividing is called : Mitosis

There are 4 main stages:

ProphaseMetaphaseAnaphaseTelophase

To remember order: Pass Me A Taco


ProphaseProphase - Nucleus goes away- The loosely coiled DNA

condenses (gets supercoiled)- forms chromosomes. You 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


Metaphase• chromosomes move to

middle of the cell

• spindle fibers, attached to the centromere of each chromosome, help the chromosomes move to the middle


Anaphase

• Each chromosome separates so that a copy of each DNA molecule moves to the poles of the cell

• Chromosomes pulled apart


Telophase• The spindle fibers disappear• A nucleus reforms• 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


Mitosis makes identical cells!!! They are clones!


Mitosis animation


Mitosis summary

How does mitosis turn one cell into two new cells?


What phase is this?

© boardworks ltd 2004 1 of 29 get notebooks 4 minutes for mission countdown use notes if needed

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