The Control of Gene Expression: Gene Expression is Controlled by a Number of Features - Gene Expression and Cancer

Question 1

What is cancer?

Answer 1

• Uncontrolled cell division that leads to the formation of tumours
• Tumours that invade and destroy surrounding tissue are called cancers

Question 2

What is a tumour?

Answer 2

• A mass of abnormal cells

Question 3

Uncontrolled cell division can lead to the formation of what types of tumours?

Answer 3

• Benign tumours

- Malignant tumours

Question 4

Malignant tumours

Answer 4

• Cancers
• Usually grow rapidly
• Invade and destroy surrounding tissues
• Cells can break off tumours and spread to other parts of the body in the bloodstream or lymphatic system (metastasis)

Question 5

What is metastasis?

Answer 5

• The process by which cells break off from a primary tumour and spread to other areas of the body, forming secondary tumours

Question 6

Benign tumours

Answer 6

• Not cancerous
• Usually grow slower than malignant tumours
• Often covered in fibrous tissue that stops cells invading other tissues
• Often harmless, but can cause blockages and put pressure on other organs
• Some benign tumours can become malignant

Question 7

How do tumour cells differ from normal cells?

Answer 7

• Nucleus is larger and darker than in normal cells
• Tumour cells sometimes have more than one nucleus
• Tumour cells have an irregular shape
• Tumour cells don’t produce all the proteins needed to function correctly
• Tumour cells have different antigens
• Tumour cells don’t respond to growth regulating process
• Tumour cells divide by mitosis more frequently

Question 8

Which types of genes control cell division?

Answer 8

• Tumour suppressor genes

- Proto-oncogenes

Question 9

Describe the role of tumour suppressor genes do and how they are affected by mutations

Answer 9

• Healthy
- Tumour suppressor genes codes for proteins that inhibits cell division by causing cells to self-destruct (apoptosis)

• Mutation

• If tumour suppressor genes mutate, gene will be inactivated
• Protein it codes for isn’t produced and cells divide uncontrollably

Question 10

What is apoptosis?

Answer 10

• Programmed cell death

- Where cells that are infected, damaged or have reached the end of their functional life are destroyed

Question 11

Describe the role of proto-oncogenes and how they are affected by mutations

Answer 11

• Healthy
- Proto-oncogenes stimulate cell division by producing proteins that result in cell division

• Mutation

• If mutated, gene can become overactive and produce more proteins
• This stimulates cells to divide uncontrollably
• A mutated proto-oncogene is called an oncogene

Question 12

What is a mutated proto-oncogene called?

Answer 12

• An oncogene

Question 13

What can lead to the formation of tumours?

Answer 13

• Mutation of tumour suppressor genes
• Mutation of proto-oncogenes into oncogenes
• Abnormal methylation of tumour suppressor genes and
  oncogenes
• Increased oestrogen concentrations in the development of
  some breast cancers

Question 14

Abnormal methylation

Answer 14

• Methylation means adding a methyl (-CH3) group onto something
• Can control whether genes are expressed (transcribed and translated)
• Hypermethylation and hypomethylation can lead to the growth of tumours

Question 15

What does hypermethylation and hypomethylation mean?

Answer 15

• Hypermethylation
- When too many methyl groups are added

• Hypomethylation
- When too little methyl groups are added

Question 16

What types of genes can experience abnormal methylation? What type of abnormal methylation of these genes can lead to the formation of tumours?

Answer 16

• Hypermethylation of tumour suppressor genes

- Hypomethylation of protons-oncogenes

Question 17

Hypermethylation of tumour suppressor genes

Answer 17

• Tumour suppressor genes aren’t transcribed
• Proteins they produce to inhibit cell division by initiating apoptosis aren’t made
• Cells are able to divide uncontrollably so tumours can develop

Question 18

Hypomethylation of proto-oncogenes

Answer 18

• Leads to proto-oncogenes acting as oncogenes
• Increases the production of proteins that lead to cell division
• Stimulates cells to divide uncontrollably so tumours are formed

Question 19

How can increased oestrogen concentrations lead to breast cancer?

Answer 19

• Exact reasons not fully understood

• Oestrogen can stimulate certain breast cells to divide

• More cell divisions mean this naturally increases the chance of mutations occurring
• If cells become cancerous, their uncontrolled cell division can be further assisted by oestrogen, helping tumours form

• Research suggests oestrogen can introduce mutations to DNA of certain breast cells
- Increases chance of cells becoming cancerous