cancer genetics Flashcards
(22 cards)
3 important cancer genes
oncogenes, tumour suppressor genes and DNA repair genes
oncogenes explained
cellular on switches that allow cells to grow and divide. One mutation is sufficient for cancer development
tumour suppressor genes explained
off switches, prevent growth. Act before DNA synthesis , two copies need to be mutated
DNA repair genes explained
rectify damage from various sources such as radiation. acts after DNA synthesis
incidence of familial breast cancer in the UK
1/8
average age of breast cancer development
61
predisposed age of onset
30-50 years old
risk of breast cancer if mutation is found
85%
main mutations in breast cancer + location
BRCA1- chromosome 17q
BRCA2- chromosome 13q
differences between BRCA1 and BRCA2 mutations
BRCA1- cumulative risk greater earlier on, ovarian cancer risk greater after 40
BRCA2- cumulative risk greater later on, greater ovarian cancer risk after age of 50
breast screening explained
mammograms, if no BRCA found annual between ages of 40-60
if BRCA found then MRI and mammograms annually from 30-50, then mammograms annually to age 70
risk reducing surgery and percentage risks
mastectomy- breast removal- less than 10& risk
ovary removal- less than 2% risk
Li Fraumeni syndrome explained
mutations in TP53 cell cycle/ tumour suppressor gene
autosomal dominant condiition with 90% penetrance
causes a variety of cell cancers
Two main bowel cancers
Familial adenomatous polyposis FAP and Lynch syndrome
explain FAP
severe mutations in APC gene, leading to a predisposition to develop hundreds of bowel polyps
cancer often in early twenties and prophylactic colectomy is recommended
Lynch syndrome explained
hereditary non-polyposis colorectal cancer
mutations in MLH1, MSH2, MSH6 PMS2
if many people in family develop bowel cancers, recurrent
screening for bowel cancer
colonoscopy, reach the ceacum, every two years for Lynch syndrome, FAP ever year
treatments
lasoo the polyps in Lynch syndrome, too many in FAP
multiple endocrine neoplasia inheritance
autosomal dominant
two types explained
Type 1- all the Ps, pituitary, pancreas and parathyroid tumours, caused by mutations in menin leading to mostly benign tumours
Type 2- caused by mutations in RET, leads to malignant tumours, medulla thyroid cancer, pheochromocytoma and parathyroid tumours
Knudson’s two hit hypothesis explained
a cell can initiate a tumour only when it has two mutant alleles, an individual who has inherited a germline mutation in a tumour suppressor gene only requires one somatic mutation, increasing their risk and age of onset
2 types of cancer testing defined
predictive- search for genetic mutations linked with a condition before you show symptoms
diagnostic testing- find out a condition associated with symptoms you already have
