Genetics Flashcards
What kind of gene mutations are heritable?
Germline mutations (mutation in an egg/sperm –> all cells in the offspring affected)
Cause inherited cancer syndromes / autosomal recessive syndromes)
What kind of gene mutations are nonheritable?
Somatic mutations
occur in non-germline tissues
Inherited cancer syndromes are caused by…
Oncogene mutations (accelerate cell division)
- 1 mutation sufficient for cancer development
- autosomal dominant inheritance
Autosomal recessive cancer syndromes are caused by mutations in…
Tumour suppressor genes
DNA damage response genes (e.g. MMR)
*2-hit-hypothesis = both genes must be affected but higher chance if 1st is inherited
Examples of inherited cancer syndromes
Familial adenomatous polyposis of colon (FAP) – 100% risk of colon cancer
Familial retinoblastoma – incomplete penetrance (skips generations)
Examples of autosomal recessive cancer syndromes
BRCA1/2 - tumour suppressor gene mutation
- breast, ovarian (+prostate) cancers
Lynch syndrome - MMR gene mutation
- colorectal, endometrial, urinary tract, ovarian and gastric cancers
Methods of genetic testing for patients with high risk of lynch syndrome
Immunohistochemistry (IHC) screening
Microsatellite instability (MSI) testing
Possible interventions for a positive genetic diagnosis of a condition
Increased awareness of symptoms/ signs
Prevention – lifestyle, avoid oestrogen, prophylactic aspirin for CRC etc…
(early/increased) screening, e.g. mammography/ colonoscopy
Prophylactic surgery, e.g. prophylactic mastectomy/ oophorectomy
The aetiology of diseases that are…
o Rare
o Genetically simple
o Unifactorial
o High recurrence rate
is usually…
Genetic
The aetiology of diseases that are…
o Common
o Genetically complex
o Multifactorial
o Low recurrence rate
is usually…
Environmental
People with a potential single gene disorder can be offered…
Pre-symptomatic Predictive Testing (PPT)
(Susceptibility testing for multifactorial diseases may become available in the future)
