GCSE · Biology · Edexcel · Spec 1BI0

Cancer as uncontrolled cell division

Cancer is what happens when a cell's division controls fail. Walk the routes below and see exactly where it goes wrong.

Biology · Cell division

From a dividing cell to a tumour

Tap a route to follow it. Each one ends somewhere different.

Are the regulating genes intact? → What kind of tumour?

Genes regulate the cell cycle. Some genes promote it and encourage division; others stop it and reduce division. Which route does this cell take?

3 routes a dividing cell can take.

On A body cell divides by mitosis. 2 branches to choose from.

Start with one body cell dividing by mitosis. Tap a route and follow it to the end.

Not all tumours are cancerous

Benign tumourvsMalignant tumour

The route split above: here is what separates the two kinds of tumour.

Focus

Is it cancer?

Benign tumour

No. It is non-cancerous.

Malignant tumour

Yes. It is cancerous.

The insight

A tumour is a mass of cells, so seeing the word 'tumour' does not tell you it is cancer. The type decides.

Where does it stay?

Benign tumour

Contained to one area, usually within a membrane. It does not invade neighbouring tissues.

Malignant tumour

It invades neighbouring tissue.

Do cells leave it?

Benign tumour

No. It stays contained.

Malignant tumour

Yes. Cells that break off spread to other parts of the body and form secondary tumours (metastasis).

Risk is not certainty

What does exposure to a risk factor mean?

Someone is exposed to a risk factor for cancer, such as smoking.

Which idea is closest to what you think right now?

If you're exposed to a risk factor like smoking, you'll definitely get cancer.Only people who have been exposed to a risk factor can get cancer.A risk factor like smoking increases the chance of getting cancer, but doesn't make it certain.

How sure are you?

I'm sureI think soI'm guessing

If you're exposed to a risk factor like smoking, you'll definitely get cancer.

This is a common misconception

It sounds logical, but it's not what risk means. A risk factor is something that increases the chances of developing the disease. Being exposed to one does not mean a person would definitely get cancer.

Only people who have been exposed to a risk factor can get cancer.

This is a common misconception

Not quite. Anyone can develop cancer. Risk factors raise the chances, but they are not the only way in.

A risk factor like smoking increases the chance of getting cancer, but doesn't make it certain.

This matches the evidence

Exactly. A risk factor increases the chances without making cancer certain, and anyone can develop cancer.

A risk factor increases the chance of cancer. It does not make cancer certain, and anyone can develop it.

Risk factors

Which risk factors are linked to which cancers?

Tick every cancer each risk factor is linked to. Some belong in two sets, and some in none of these three.

A Linked to bowel cancer
B Linked to liver cancer
C Linked to cervical cancer

Smoking
Obesity
Hepatitis B and C infection
HPV infection
UV radiation (sun, sunbeds)
Inherited genes

Your turn

Explain it in your own words

Explain how a change in the DNA of a cell can lead to the formation of a tumour. [4 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

Some genes promote the cell cycle (encourage cell division) and other genes stop it (reduce cell division), so the cell cycle is regulated. (1 mark)
DNA is damaged / changed, and some of the genes that regulate cell division are changed. (1 mark)
Cells start to divide uncontrollably. (1 mark)
A mass of cells, a tumour, forms. (1 mark)

Model answer

Genes regulate the cell cycle: some promote cell division and others stop it, so cells divide only when they need to. If the DNA is damaged and some of these regulating genes are changed, the cells divide uncontrollably. The extra cells build up into a mass of cells, which is a tumour.

Regulating genes working means controlled division. Regulating genes changed means uncontrolled division, and a tumour can form.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

What you need to know

Mitosis is cell division that makes genetically identical cells, which the body needs for growth and repair of damaged tissue.
Mitosis is part of the cell cycle, and genes regulate that cycle so cells divide only when they need to.
Some genes promote the cell cycle and encourage division; others stop it and reduce division, and defective cells self-destruct.
Have a goYour friend says, totally confidently: 'Genes only ever tell cells to divide more.' What would you tell them?
Some genes do the opposite: they stop the cell cycle and reduce division.
The tempting answer forgets the stopping genes. Regulation needs both kinds, and it also makes defective cells self-destruct.
Cancer is caused by changes to the DNA of a cell that lead to uncontrolled cell growth and division.
If some genes that regulate division are changed, cells divide uncontrollably and can form a tumour, which is a mass of cells.
Tumour cells keep dividing, while the healthy cells around them still have controlled division.
Have a goA tumour is growing. Before you read on, predict: are the healthy cells right next to it also dividing out of control?
No. Only the tumour cells have lost control; the healthy cells nearby still have controlled division.
It is tempting to picture the whole area going wrong, but the change is in the tumour cells, not their neighbours.
Not all tumours are cancerous: a benign tumour is non-cancerous and usually contained within a membrane, not invading neighbouring tissues.
A malignant tumour is cancerous: it invades neighbouring tissue, and cells that break off form secondary tumours, called metastasis.
Anyone can develop cancer; a risk factor increases the chances, but exposure does not mean a person would definitely get it.
Lifestyle risk factors include smoking, obesity, UV radiation and viral infections; genetic risk factors are inherited genes a person is born with.
Have a goPick the genetic one: smoking, inherited genes or UV radiation?
Inherited genes.
A genetic risk factor is a gene you are born with. Smoking and UV radiation come from outside the body, so they are lifestyle risk factors.

The big picture

Genes regulate the cell cycle so cells divide only when they need to. If DNA damage changes some of those genes, cells divide uncontrollably and form a tumour. Benign tumours stay contained and are non-cancerous; malignant tumours invade and spread by metastasis. Risk factors raise the chance of cancer but never make it certain.

Key points

1Genes regulate the cell cycle: some promote division, others stop it, and defective cells self-destruct.

2Cancer is caused by changes to the DNA of a cell that lead to uncontrolled cell growth and division.

3Uncontrolled division can form a tumour, a mass of cells, while the healthy cells around it stay under control.

4Benign tumours are non-cancerous and contained; malignant tumours are cancerous, invade and spread by metastasis.

5A risk factor increases the chance of cancer but does not make it certain, and anyone can develop cancer.

.we-_R_18slubsnpfiv5ubrb_ [data-we-step]{display:flex !important}.we-_R_18slubsnpfiv5ubrb_ [data-we-solution]{display:block !important}.we-_R_18slubsnpfiv5ubrb_ [data-we-reveal]{display:none !important}

Worked example

Problem

A scan shows a tumour. Its cells have pushed into the tissue next to it, and some cells have left and started new tumours in a different part of the body. Benign or malignant? And what is that spread called?

⚠ Watch out

Thinking every tumour is cancer, or that being exposed to a risk factor means a person will definitely get cancer. Only malignant tumours are cancerous, and a risk factor only increases the chance.

🧠

Memory hook

Benign stays home; malignant roams. And a risk factor shifts the odds. It never fixes the result.

✓

Check yourself

Cover the page and explain to an imaginary friend how changed genes can end up as a tumour that spreads.

Flashcards

(14)

What is mitosis?

A type of cell division that produces genetically identical cells. Most body cells use it, for growth and repair of damaged tissue.

How do genes control the cell cycle?

They regulate it so cells divide only when they need to. Some genes promote the cycle and encourage division; others stop it and reduce division.

What happens to defective cells when the cell cycle is regulated properly?

They self-destruct.

What causes cancer?

Changes to the DNA of a cell that lead to uncontrolled cell growth and division.

What is a tumour?

A mass of cells that forms when cells divide uncontrollably.

What do the healthy cells around a tumour do?

They keep dividing in a controlled way, while the tumour cells continue to divide uncontrollably.

What is a benign tumour?

A non-cancerous tumour, contained to one area (usually within a membrane), that does not invade neighbouring tissues.

What is a malignant tumour?

A cancerous tumour that invades neighbouring tissue. Cells that break off can spread and form secondary tumours.

What is metastasis?

Cells breaking off a malignant tumour, spreading to other parts of the body and forming secondary tumours.

What is a risk factor?

Something that increases the chances of developing a disease. Exposure does not mean a person would definitely get cancer.

Name the four lifestyle risk factors for cancer from this lesson.

Smoking, obesity, UV radiation and viral infections.

What is a genetic risk factor?

Inherited genes that a person is born with that increase their chances of developing cancer.

Which cancers is smoking linked to?

Lung cancer mainly, and also mouth, bowel, stomach and cervical cancer. Cigarette smoke contains carcinogenic chemicals.

Which viral infections are risk factors, and for which cancers?

HPV is linked to cervical cancer. Hepatitis B and C are linked to liver cancer.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

Learning with Lightbulb is opening soon

You can use this lesson now. Join the waitlist and we'll let you know when the full Lightbulb experience is ready.

Keep me posted

From a dividing cell to a tumour

What does exposure to a risk factor mean?

Which risk factors are linked to which cancers?

Explain it in your own words

More Edexcel GCSE Biology topics