A3. Cancer

Question 1

Cell division and cancer
Mutations that occur in individual cells after fertilisation (e.g. in adulthood) are called ___________ ___________. If these mutations occur in the genes that control the rate of cell division (by mitosis), it can cause uncontrolled cell division. If a cell divides uncontrollably the result is a tumour - (which is..?).

Tumours that invade and destroy surrounding tissue are called ________
There are two types of gene that control cell division - ________ _____________ ______ and ______-_____________. __________in these genes can cause cancer.

Answer 1

Mutations that occur in individual cells after fertilisation (e.g. in adulthood) are called acquired mutations. If these mutations occur in the genes that control the rate of cell division (by mitosis), it can cause uncontrolled cell division. If a cell divides uncontrollably the result is a tumour - a mass of abnormal cells.

Tumours that invade and destroy surrounding tissue are called cancers.
There are two types of gene that control cell division-tumour suppressor genes and proto-oncogenes. Mutations in these genes can cause cancer.

Question 2

Tumour suppressor genes - When normal vs when mutated?

Answer 2

When Normal

When functioning normally, tumour suppressor genes slow cell division by producing proteins that stop cells dividing or cause them to self-destruct (apoptosis)

When mutated

If a mutation occurs in a tumour suppressor gene, the gene will be inactivated. The protein it codes for isn’t produced and the cells divide uncontrollably (the rate of division increases) resulting in a tumour

Question 3

Proto-oncogenes - When normal vs when mutated?

Answer 3

When Normal

When functioning normally, proto-oncogenes stimulate cell division by producing proteins that make cells divide

When mutated

If a mutation occurs in a proto-oncogene, the gene can become overactive. This stimulates the cells to divide uncontrollably (the rate of division increases) resulting in a tumour.

A mutated proto-oncogene is called an oncogene.

Question 4

Tumours and cancers

Tumours can develop for years without any obvious symptoms and can be quite large by the time they’re discovered. Not all tumours are cancerous-
there are two different types: (explain them)

Answer 4

1. Malignant tumours

• Malignant tumours are cancers.
• They usually grow rapidly and invade and destroy surrounding tissues.
• Cells can break off the tumours and spread to other parts of the body in the bloodstream or lymphatic system.

2. Benign tumours

• Benign tumours are not cancerous.
• They usually grow slower than malignant tumours and are often covered in fibrous tissue that stops cells invading other tissues.
• Benign tumours are often harmless, but they can cause blockages and put pressure on organs. Some benign tumours can become malignant.

Question 5

Tumour cells can differ from normal cells in many different ways (6 things)

Answer 5

• The nucleus is larger and darker than in normal cells. Sometimes the cells have more than one nucleus.
• They have an irregular shape.
• They don’t produce all the proteins needed to function correctly.
• They have different antigens on their surface.
• They don’t respond to growth regulating processes.
• They divide (by mitosis) more frequently than normal cells.

Question 6

Tip: You need to understand the difference between benign and malignant. You should never say ________cancers there’s no such thing. Only ___________tumours are cancerous.

Answer 6

Tip: You need to understand the difference between benign and malignant. You should never say benign cancers there’s no such thing. Only malignant tumours are cancerous.

Question 7

Causes of tumour growth
There are a number of different factors that are thought to lead to the growth of tumours. These include (2 things first thing when normal/bad, 2nd thing its role)

Answer 7

Methylation - When normal

• Methylation means adding a methyl group onto something.
• Methylation of DNA is an important method of regulating gene expression it can control whether or not a gene is transcribed (copied into mRNA) and translated (turned into a protein).
• When methylation is happening normally, it plays a key role in many processes in the body.

Abnormal Methylation

• It’s only when it happens too much (hypermethylation) or too little (hypomethylation) that it becomes a problem.
• The growth of tumours can be caused by abnormal methylation of certain cancer-related genes.

Oestrogen

• Oestrogen can stimulate certain breast cells to divide and replicate. The fact that more cell divisions are taking place naturally increases the chance of mutations occurring, and so increases the chance of cells becoming cancerous.
• Oestrogen’s ability to stimulate division could also mean that if cells do become cancerous, their rapid replication could be further assisted by oestrogen, helping tumours to form quickly.
• Other research suggests that oestrogen is actually able to introduce mutations directly into the DNA of certain breast cells, again increasing the chance of these cells becoming cancerous.

Question 8

Tip: HRT stands for hormone replacement therapy. It is used to increase ____________(and usually also progesterone) levels in some women in order to treat symptoms experienced during the ____________(the end of menstruation).

Answer 8

Tip: HRT stands for hormone replacement therapy. It is used to increase oestrogen (and usually also progesterone) levels in some women in order to treat symptoms experienced during the menopause (the end of menstruation).

Question 9

Risk factors for cancer
There’s no single cause for cancer but scientists have identified lots of different ‘risk factors’ - things that ________ a person’s ________of getting cancer.

(2 risk factors)

Answer 9

Risk factors for cancer
There’s no single cause for cancer but scientists have identified lots of different ‘risk factors’ - things that increase a person’s chance of getting cancer. Risk factors can be either genetic or environmental

Genetic factors

• Some cancers are linked with specific inherited allele (a version of a gene).
• If you inherit that allele you’re more likely to get that type of cancer (but it doesn’t mean you’ll definitely get that type of cancer).

Example
Hereditary mutations of the gene BRCA1 can greatly increase the chance of a woman developing breast cancer in her lifetime.

Environmental factors

• Exposure to radiation, lifestyle choices such as smoking, increased alcohol consumption, and a high-fat diet have all been linked to an increased chance of developing some cancers.