Cancer — AQA GCSE Biology
Test yourself on Cancer with AQA GCSE practice questions.
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Cancer explained
Cancer develops when changes occur in the DNA of a cell, altering the way the cell divides.
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Normally, cell division is controlled so that new cells are produced only when needed. In cancer, these control mechanisms fail, so the cell divides repeatedly and uncontrollably. The resulting mass of abnormal cells is a tumour. If the tumour invades nearby tissues and spreads to other parts of the body, it is malignant; benign tumours do not invade or spread in the same way. Risk factors such as smoking, radiation and some viruses increase the chance of the DNA changes that can start cancer.
Benign tumours are growths of abnormal cells which are contained in one area, usually within a membrane. They do not invade other parts of the body.
A benign tumour is a mass of abnormal cells that stays in the place where it first formed. The cells divide in an uncontrolled way, but the resulting growth is contained in one area, usually enclosed within a membrane. Because it remains localised, it does not invade neighbouring tissues and does not travel in the blood to form tumours elsewhere. A common example is a mole or wart on the skin: it may enlarge slowly and can be removed, but it does not spread through the body. Benign tumours are not described as cancerous, although a large one can still cause problems by pressing on nearby organs or tissues. Contrast this with a malignant tumour, which invades and spreads.
Malignant tumour cells are cancers. They invade neighbouring tissues and spread to different parts of the body in the blood where they form secondary tumours.
A malignant tumour is a cancer. Its cells divide uncontrollably and are not contained within a membrane, so they can break into neighbouring tissues and destroy them. Cells can also detach from the primary tumour and enter the bloodstream. Blood carries them around the body, and where they settle in another organ they divide to form a secondary tumour. This spreading process is called metastasis. For example, a primary tumour in the lung can release cells that travel in the blood and form secondary growths in the liver or brain. Because malignant cells reach many sites, treatment is more difficult than for a benign growth, and early detection improves the chance of successful treatment.
Scientists have identified lifestyle risk factors for various types of cancer.
A risk factor is something that increases the chance of developing a disease, but it does not guarantee that the disease will occur. Scientists study large groups of people over long periods and compare those exposed to a factor with those not exposed. In this way they have identified lifestyle risk factors for various types of cancer. Lifestyle factors are aspects of a person's behaviour or environment that they may be able to change. Examples include smoking, which is linked to lung cancer; drinking too much alcohol, linked to liver cancer; obesity and a poor diet; and exposure to ultraviolet radiation from the Sun or sunbeds, linked to skin cancer. Reducing exposure to these factors lowers risk, but because risk is not certainty, a person with no known risk factors can still develop cancer.
There are also genetic risk factors for some cancers.
Not all risk of cancer comes from lifestyle. Some people inherit gene variants, sometimes called faulty genes, that increase the chance of developing particular cancers. These inherited factors are genetic risk factors. For example, variants of the BRCA1 and BRCA2 genes are linked to a higher risk of breast and ovarian cancer, and some inherited gene changes increase the risk of bowel cancer. A genetic risk factor is present from birth and cannot be changed by behaviour, although it still only raises the probability of cancer rather than making it certain. Scientists identify these factors by studying family histories and comparing the DNA of people with and without a particular cancer. Knowing about a genetic risk can guide screening and earlier monitoring.
Your focus
- Describe cancer as a result of changes in cells.
- Explain how changes in cells lead to uncontrolled growth and division.
- Relate risk factors to the development of cancer.
Show all 15 objectives
- State that a benign tumour is a growth of abnormal cells contained in one area.
- Explain that benign tumours do not invade other parts of the body or spread in the blood.
- Distinguish benign tumours from malignant tumours using the ideas of containment and spread.
- State that malignant tumour cells are cancers.
- Describe how malignant cells invade neighbouring tissues and spread in the blood.
- Explain how secondary tumours form at different sites in the body.
- Define a lifestyle risk factor for cancer.
- Give examples of lifestyle risk factors and link each to a type of cancer.
- Explain that risk factors increase the chance of cancer without making it certain.
- State that some cancers have genetic risk factors.
- Give an example of an inherited gene variant linked to a type of cancer.
- Explain that genetic risk factors increase the chance of cancer without making it certain.
Cancer exam tips
Marking Points
- States that cancer results from changes in cells, often described as changes to DNA or genes.
- Explains that these changes cause uncontrolled growth and division of cells.
- Describes the formation of a tumour as a mass of abnormal cells.
- Distinguishes malignant tumours, which invade and spread, from benign tumours, which do not.
- Links risk factors such as smoking or radiation to an increased chance of the cell changes that cause cancer.
- Uses correct terminology such as cell division, uncontrolled growth and tumour.
- Benign tumours are growths of abnormal cells, meaning cell division has gone wrong but the cells remain grouped together.
- The growth is contained in one area and is usually enclosed within a membrane.
- Benign tumour cells do not invade neighbouring tissues.
- Benign tumour cells do not travel in the blood to other parts of the body, so no secondary tumours form.
- Benign tumours are not cancers, although they can still damage health by pressing on surrounding structures.
- Malignant tumour cells are cancers, formed by uncontrolled cell division.
- Malignant cells invade neighbouring tissues and can damage them.
- Cells can break away and travel to other parts of the body in the blood.
- A tumour that forms at a new site is a secondary tumour.
- The spread of malignant cells makes treatment more difficult than for a benign tumour.
- A risk factor increases the chance of developing cancer but does not make it certain.
- Lifestyle risk factors are linked to behaviour or environment and can often be changed.
- Examples include smoking, excess alcohol, obesity, poor diet and ultraviolet radiation.
- Scientists identify risk factors by studying large populations over time and comparing groups.
- Reducing exposure to a lifestyle risk factor lowers the chance of developing the associated cancer.
- Genetic risk factors are inherited gene variants that increase the chance of certain cancers.
- They are present from birth and cannot be changed by lifestyle choices.
- Examples include inherited variants of the BRCA genes linked to breast and ovarian cancer.
- A genetic risk factor raises the probability of cancer but does not make cancer certain.
- Scientists identify genetic risk factors by studying family histories and comparing DNA between groups.
Examiner Tips
- 💡Use the phrase uncontrolled growth and division when describing cancer.
- 💡Link the description to cell changes, such as changes in DNA, rather than saying cells simply grow.
- 💡If asked about risk factors, name a specific factor and explain how it increases the chance of cell changes.
- 💡Use the phrase contained in one area when explaining why a benign tumour is not cancer.
- 💡Link each feature to the outcome: no invasion and no spreading means no secondary tumours.
- 💡If asked to compare, set out benign and malignant features side by side rather than describing only one type.
- 💡Name the transport system explicitly: cells spread in the blood.
- 💡Use the term secondary tumour when describing growth at a new site.
- 💡Sequence the process: uncontrolled division, invasion, entry into blood, settlement, secondary tumour.
- 💡Define risk factor before giving examples, so the meaning is clear.
- 💡Match each example to a named cancer type, such as smoking and lung cancer.
- 💡Use words such as increases the chance rather than causes when writing about risk factors.
- 💡Use the word inherited when describing genetic risk factors.
- 💡Give a named example, such as BRCA gene variants and breast cancer, to support the point.
- 💡State clearly that genetic risk increases probability rather than causing cancer with certainty.
Common Mistakes
- Saying cancer is a single disease caused by one pathogen; correct this by explaining that cancer arises from changes in cells and has many forms.
- Confusing benign and malignant tumours; correct this by stating that malignant tumours invade and spread, while benign tumours do not.
- Stating that all tumours are cancerous; correct this by explaining that a tumour is a mass of abnormal cells and may be benign or malignant.
- Saying a benign tumour is harmless in every case; correction: it does not spread, but it can still press on organs and cause problems.
- Confusing benign with malignant and claiming benign tumours spread in the blood; correction: only malignant tumours invade and spread.
- Describing a benign tumour as a group of normal cells; correction: the cells are abnormal, but the growth stays localised.
- Saying malignant cells travel in the blood but omitting that they form secondary tumours; correction: state both transport and the new growth.
- Using the words benign and malignant as if they were interchangeable; correction: only malignant tumours are cancers and only they invade and spread.
- Claiming that a secondary tumour is a new, unrelated cancer; correction: it formed from cells of the original primary tumour.
- Treating a risk factor as a definite cause; correction: it raises the probability of cancer but does not guarantee it.
- Listing only smoking; correction: give a range of examples such as alcohol, obesity, diet and ultraviolet radiation.
- Confusing correlation with proof of cause; correction: population studies show a link, and scientists look for further evidence before calling something a cause.
- Saying a genetic risk factor guarantees cancer; correction: it increases the chance, and many people with the variant never develop cancer.
- Confusing genetic risk factors with lifestyle risk factors; correction: genetic factors are inherited, whereas lifestyle factors relate to behaviour and environment.
- Claiming all cancers are inherited; correction: only some cancers have identified genetic risk factors, and most cancers involve a combination of factors.