Gene Expression And Cancer

Question 1

What is a tumour?

Answer 1

A clump/mass of cells that undergo rapid and uncontrolled cell division

Question 2

What is cancer

Answer 2

• Mutant cells - different from normal cells.
• Structurally and functionally
• Most mutated cells die but some survive, make clones of themselves and form either benign or malignant tumours.

Question 3

Benign meaning

Answer 3

Tumours don’t spread

Question 4

Malignant meaning

Answer 4

Tumours can spread

Question 5

What is proto-oncogenes?

Answer 5

stimulate cell growth (car accelerator pedal)

Question 6

What are tumour suppressor genes

Answer 6

slow cell division (car brake pedal)

Question 7

What do proto-oncogenes code for

Answer 7

-growth factors
-receptors

Question 8

proto-oncogene mutation

Answer 8

Mutâtes to oncogene
1.increasing growth factor
•more binds to receptors leads to more transcription
2.receptor mutation
•more transcription factors and rna polymerase binding
•more transcription

Question 9

Proto-oncogene model answer

Answer 9

Mutation changes the proto-oncogene into an oncogene;
*Receptor protein permanently activated
•Oncogene may code for a growth factor that is produced in large amounts
• Excessive uncontrolled cell division

Question 10

Tumour suppressor gene mutation due to

Answer 10

-change in base sequence
-decrease acetylation
-increased methylation

Question 11

Tumour suppressor gene model answer

Answer 11

•Mutation changes the sequence of the bases in the tumour suppressor gene.
•Tumour suppressor gene is no longer transcribed or tertiary structure of protein is altered
•Cell division is no longer controlled
•This is often caused by increased methylation, but we’ll get to that when we do epigenetics)

Question 12

How does oestrogen switch on gene expression

Answer 12

Oestrogen is a steroid hormone so is lipid soluble so diffuses across the phospholipid bilayer
•Oestrogen binds to the complementary receptor on the transcription factor
• Binding causes a change in the tertiary structure
• The transcription factor moves into the nucleus through the nuclear pore
• The transcription factor can now bind to a specific promoter base sequence of DNA
• Binding of the transcription factor switches the gene on by encouraging
RNA polymerase to bind and starting transcription

Question 13

Oestrogen and breast cancer