L5 - Control of cell division & tumours

Question 1

Define a tumour

Answer 1

An abnormal mass of cells

Question 2

State the two types of tumour

Answer 2

Benign and malignant (cancerous)

Question 3

Benign or malignant?

Mitosis occurs in the middle of the tumour, so clearly defined boundary

Answer 3

Benign

Question 4

Benign or malignant?

Mitosis occurs at the edges of the tumour, so no clearly defined boundary

Answer 4

Malignant

Question 5

Benign or malignant?

Metastasis doesn’t occur

Answer 5

Benign

Question 6

Benign or malignant?

Cells can break off, causing secondary tumours to develop elsewhere in the body (metastasis)

Answer 6

Malignant

Question 7

Benign or malignant?

Slow-growing

Answer 7

Benign

Question 8

Benign or malignant?

Fast growing

Answer 8

Malignant

Question 9

Tumour suppressor genes =

Answer 9

The brake pedal to cell division

Question 10

Proto-oncogenes =

Answer 10

The accelerator pedal to cell division

Question 11

What do tumour suppressor genes code for?

Answer 11

Proteins that repair DNA or cause apoptosis (programmed cell death)

Question 12

Define apoptosis

Answer 12

Programmed cell death

Question 13

What occurs if a tumour suppressor gene mutates?

Answer 13

If they mutate, the new allele will code for a non-functioning protein. The rate of cell division will increase, resulting in a tumour

Question 14

Mutated tumour suppressor genes =

Answer 14

‘Recessive cancer genes’ because 2 mutations in tumour suppressor genes are required for cancer to occur.

Question 15

What do proto-oncogenes code for?

Answer 15

They code for cellular signalling proteins that increase the rate of cell division when growth factors bind to receptors on the cell surface membrane

Question 16

What do mutated proto-oncogenes become?

Answer 16

Oncogenes (‘onco’ = cancer). They code for proteins that work WITHOUT the need for the growth factors

Question 17

Oncogenes = _____ cancer genes because…

Answer 17

Oncogenes = dominant cancer genes because it only takes a mutation in one allele of a proto-oncogene to make an oncogene

Question 18

Acetyl groups act on _____ and ____ transcription

State the memorable phrase

Answer 18

Acetyl groups act on HISTONES and INCREASE transcription

Remember: Acetyl = Add

Question 19

Methyl groups act on _____ and ____ transcription

State the memorable phrase

Answer 19

Methyl groups act on DNA itself and DECREASE transcription

Remember: Methyl = Minus

Question 20

Describe hypERmethylation of tumour suppressor genes

3 points

Answer 20

The genes cannot be transcribed

So the proteins they produce to slow cell division aren’t made

Therefore cells are able to divide uncontrollably by mitosis and tumours can develop

Question 21

Describe hypOmethylation of proto-oncogenes

3 points

Answer 21

This causes them to act as oncogenes

Increases the production of the proteins that encourage cell division.

Stimulates cells to divide uncontrollably, causing the formation of tumours

Question 22

State three reasons a woman could have increased exposure to oestrogen

Answer 22

1) Periods starting early
2) Late menopause
3) Taking HRT (Hormone replacement therapy - an oestrogen-containing drug)

Question 23

State the relationship between oestrogen exposure and risk of developing breast cancer

Answer 23

Increased exposure to oestrogen = Increased risk of breast cancer.

Positive correlation

Question 24

State three possible theories as to how oestrogen can contribute to the development of some breast cancers

Answer 24

1) Oestrogen causes proto-oncogenes –> oncogenes in breast tissue
2) Oestrogen increases transcription of cell division genes in breast tissue (more cells = more chance of cancer)
3) Post-menopause, despite oestrogen levels falling, fat cells in breast tissue produce oestrogen. (Amazing)