genetic predisposition to cancer Flashcards
genetic processes associated with cancer
- the activation of oncogenes
- the deactivation of tumour suppressor genes
- the abnormal working of of DNA damage-response genes
proto-oncogene
normal gene that codes for proteins to rgeulate cell growth and differentiation
what changes a proto-oncogene into an oncogene?
mutation
how many ‘hits’ are required for oncogenes to cause cancer
only one mutation in the gene on one chromosome is required
how many ‘hits’ are required for tumour supressor genes to cause cancer?
2 mutations are required, one in each of the genes on each chromosome
what are DNA damage-response genes?
The repair mechanics for DNA
how many ‘hits’ are required to cause cancers due to DNA damage-response genes ?
two hits are required, one in each copy of the gene, this speeds the accumulation of other mutations in critical areas
what is miss match repair?
occurs when there is a base pair miss match, eg. T is paired with C in DNA replication. Repair mechanisms are used to fix this abnormality.
what happens if there is defective miss match repair mechanisms?
risk of cancer forming
what can microsatellite instability tell us?
that there is a problem with miss match repair
dysplastic tumour
A tumour that is benign but could progress to malignancy
example of oncogene
RET
example of tumour supressor gene
- BRCA1 and BRCA 2
- RB
what does a loss of function in BRCA 1 or BRCA2 cause?
breast cancer
what does a loss of function in RB gene cause?
retinoblastoma
what does activation of the RET gene cause?
MEN2 multiple endocrine neoplasia
examples of DNA repair genes and what do they cause?
MLH1, MSH2, MSH6, PMS1, PMS2
hereditary non-polyposis colon cancer
what is a de novo mutation?
a mutation that occurs in germ cell of a parent, there is no family history of the cancer syndrome
main risk factors foe breast cancer
- ageing
- family history
- dietary factors eg. alcohol
- lack of excersise
example of autosomal recessive syndromes
MYH polyposis
risk factors for colorectal cancer
- ageing
- personal history of colorectal cancer or adenomas
- high fat, low-fibre diet
- inflammatory bowel disease
- family history of CRC
what is predictive gene testing?
test carried out to determine a patient’s risk of developing a cancer
