Gene expression and cancer

Question 1

What are malignant tumours?

Answer 1

• large
• rapid growth
• darker
• large nucleus
• unspecialised
• spread to other areas
• form secondary tumours
• no capsule so can grow projections into surrounding tissue
• abnormal tumour tissue replaces normal tissue
• cancerous

Question 2

What is cancer?

Answer 2

• cancer cells are derived from a single mutant cell
• the initial mutation causes uncontrolled mitosis in this cell caused by damage to the genes that regulate mitosis and the cell cycle

Question 3

What are oncogenes?

Answer 3

• most oncogenes are mutations of proto-oncogenes which stimulate a cell to divide when growth factors attach to a protein receptor on its cell-surface membrane
• this then activates genes that cause DNA to replicate and the cell to divide
• if a proton-oncogene mutates into an oncogene it may become permanently activated
• the result is that cells divide too rapidly and out of control, and a tumour or cancer, develops
• this can be caused by inherited or environmental factors

Question 4

What are Proto-onco genes?

Answer 4

• the receptor protein on tone cell-surface membrane can be permanently activated, so that cell division is switched on even in the absence of growth factors
• the oncogene may code for a growth factor that is then produced in excessive amounts, again stimulating excessive cell division

Question 5

What are tumour suppressor genes?

Answer 5

• tumour suppressor genes slow drown cell division, repair mistakes in DNA, and ‘tell’ cells when to die which prevents the formation of tumours
• if a tumour suppressor gene becomes mutated it is inactivated, it stops inhibiting cell division anew cells grow out of control
• while most of these die, those that survive can make clones of themselves and form tumours

Question 6

What is hypomethylation?

Answer 6

-hypomethylation has been found to occur in oncogenes where it leads to their activation and hence the formation of tumours

Question 7

what is hypermethylation?

Answer 7

• hypermethylation leads to the tumour suppressor gene being inactivated
• as transcription of tumour suppressor genes is inhibited which switches them off
• as the tumour suppressor gene normally slows the rate of cell division, its inactivation leads to increased cell division and the formation of a tumour

Question 8

How does oestrogen cause breast cancer?

Answer 8

• increased oestrogen production in the breast post menopause may lead to uncontrolled mitosis
• once a tumour has developed, it further increases oestrogen concentration which therefore leads to increased development of the tumour
• it also appears that white blood cells that are drawn to the tumour increase oestrogen production which leads to the development to even greater development of the tumour

Question 9

What are the scientific lifestyle factors that contribute to cancer?

Answer 9

• smoking
• diet
• obesity
• physical activity
• sunlight

Question 10

what are the differences between benign and malignant tumors?

Answer 10

• benign tumours tend to have localised effects of the body where as malignant tumours often have systematic (whole body) effects such as weight loss and fatigue
• benign tumours can usually be recovered by surgery alone where as malignant tumours removal usually involved radiotherapy and/or chemotherapy as well as surgery
• benign tumours rarely reoccur after treatment where as malignant tumours more frequently reoccur after treatment

Question 11

What are benign tumours?

Answer 11

• large
• slow growing
• normal looking
• specialised
• adhesion factors mean they stay in one place
• primary tumours
• capsule
• dense tissue
• compact
• non canerous
• can disrupt vital organ function

Question 12

what is he difference between tumour suppressor genes and oncogenes?

Answer 12

-oncogenes cause cancer as a result of the activation of proto-oncogenes, tumour suppressor genes cause cancer when they are inactivated

Question 13

What does cancer screening detect?

Answer 13

• oncogene mutations, which can determine the type of cancer that the patient has and hence the most effective drug or radiotherapy to use
• gene changes that predict which patients are more likely to benefit from certain treatments and have the best chance of survival
• for example, the drug perception is most effective at treating certain types of breast cancer
• a single cancer cell among millions of normal cells, thus identifying patients at risk of relapse from certain forms of leukaemia