Gene expression and cancer

cancer is

a group of diseases caused by damage to genes that regulate mitosis and control cell division

malignant (cancerous) features

• grow to large size

• grow rapidly

• not produce adhesion molecules so can spread to other regions

• removal involves chemotherapy

• can become unspecialised

benign (non cancerous) features

• grow large size

• grow very slowly

• well differentiated

• produce adhesion molecules so they stick together

• can usually be removed

oncogenes are causes by

mutation of proto-oncogenes

what do proto-oncogenes stimulate

a cell to divide when a growth factor attaches to a protein receptor on its cell surface membrane. This activates gene and dna replicates.

oncogenes cause cells to be

permanently activated

why are oncogenes permeantly activated

• receptor protein on cell surface membrane is permanently activated, so cell division continues with absence of growth factors

• may code for growth factor that is produced in excessive amounts

• rapidly divide

tumour suppressor genes

slow down cell division

what is programmed cell death called

apoptosis

what happens when tumour suppressor gene gets mutated

it becomes inactivated and stops inhibiting cell division

difference between oncogenes and tumour suppressor genes

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

how does hypermethylation occur (increases)

• occurs in promoter region of tumour suppressor genes

• inactivated

• transcription of promoter region of tumour suppressor gene is inhibited

• gene is silenced

• increased cell division and tumour formation

where does hypomethylation occur

in oncogenes