Cell Division Lesson 3

National 4 Cell Biology Unit

Starter - Create a question that uses one of the words below as the answer and write it on a sticky note. Your teacher will ask a

selection of these questions to the class!

Learning Intentions

• To look at the basic concept of how the cell cycle is controlled and how this links to cancer.

• To research a type of cancer and present your findings appropriately.

Success Criteria

• I can describe where there are checkpoints in the cell cycle and explain what the cell is checking at each checkpoint.

• I can link this to our understanding of how tumour cells form and how this can lead to cancer.

• I can research a type of cancer and present my findings.

The Cell Cycle

• As you can see the cell only spends a little of it’s time in mitosis (M Phase). Most of the time it is in one of the two Growth (G) Phases where it grows and does its normal cell functions!

Second Growth Phase

First Growth Phase

DNA Synthesis

What happens in each phase?• First Growth Phase - Cell grows and increases in mass

by adding cytoplasm, cell membrane and cell wall (if it is a plant). The materials needed for DNA replication are made.

• DNA Synthesis phase – DNA is replicated. We’d see the chromosomes replicate and become chromtids.

• Second Growth Phase - It’s another period of growth. The cell builds up an energy reserve to last it through the rest of the process and proteins necessary for cell division are made.

• Mitosis Phase – Mitosis takes place and cell divides.

Need for Checkpoints

• We know that it is important that each new cell produces is identical to the parent cell and can perform the same function.

• The cell self checks at THREE stages to make sure that it is ready to proceed.

• If the cell is not ready then it should not proceed to the next stage and if there is something wrong then the cell should not divide at all but should be destroyed!

What are the checkpoints?• End of First Growth Phase.

Checking the Cell Size – is the cell big enough to continue? Yes – go to S phase!

• End of Second Growth Phase. Has the DNA been copied correctly? Is DNA replication complete? Has the cell enough energy/materials to continue. Yes – can enter mitosis!

• During mitosis, have the chromatids been pulled apart correctly? Then the cell can divide!

1st Growth Phase

2nd Growth Phase

DNA Synthesis

Original Work

The Nobel Prize in Physiology or Medicine 2001• The Nobel Prize in Physiology or Medicine was

jointly awarded to Leland Hartwell, Tim Hunt and Paul Nurse for their discoveries of "key regulators of the cell cycle".

• Using genetic and biochemical methods, they identified the molecules that control the cell cycle in eukaryotic organisms.

• These fundamental discoveries have a profound impact on many aspects of biology and medicine.

What would happen if the controls failed?

What goes wrong in Cancer?

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Increased cell division = more cells

Decreased cell death = more cells

Loss of contact inhibition – the cells no longer stay in one place

Ability to invade surrounding tissues

Ability to move - metastasis

Loss of DNA Repair

Escape from immune surveillance = cells not destroyed

Cancer cells – Research Task1. Find out the meaning of the following terms…• Benign• Malignant• Metastasis2. Research a type of cancer and find out the following:• What part of the body does this cancer affect?• What are the clinical symptoms?• How common is this cancer (in the UK)?• What is the treatment given for this cancer?• What research is being done on this cancer? • Is there a charity fundraising to help support people

affected by this type of cancer?

What goes wrong in Cancer?

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Increased cell division = more cells

Loss of contact inhibition – the cells no longer stay in one place

Ability to move - metastasis