Genetics 4-5 Flashcards
(38 cards)
What is a silent mutation?
Change in the third nucleotide but does not cause a change in the amino acid translated.
What is a driver mutation?
The first mutation that causes the cell to change from normal to a mutated cancerous cell.
What is a tumour-suppressor gene?
Acts as a cell cycle regulator and as the stop signal. Controls mitosis so it does not lead to uncontrolled growth.
What are photo-oncogenes?
Opposite of tumour suppressor genes. Promote growth and proliferation. Normally growth factors, transcription factors or tyrosine kinases.
What does Knudson’s two-hit hypothesis state?
That mutations in both alleles of a gene are needed to cause a disease. Hit 1 is normally a point mutation whereas hit 2 is normally a deletion, causing total loss of transcription and giving rise to malignancy potential.
What is retinoblastoma?
A checkpoint protein between G1 and S phase which normally binds to E2F (transcription factor) to prevent growth factor release.
What happens in the case of mutant retinoblastoma?
Retinoblastoma can’t properly bind to E2F so growth signals are produced, possibly causing malignancy.
What mutations can cause inherited breast cancer?
BRCA1 and BRCA2 germline (less common)
What are healthy BRCA genes responsible for?
Normally are tumour suppressor genes but when mutated they lose the ability to stop the cell cycle.
What does the BRCA mutations also predispose an individual to?
Ovarian cancer
How does the BRCA mutations change risk to breast cancer?
Increases lifetime risk up to 60% of developing breast cancer before the age of 90.
What conditions can predispose an individual to colorectal cancer?
Adenomatous polyposis and Lynch syndrome
What is the risk of developing colorectal cancer if they have predisposing conditions?
Almost 100% lifetime risk
What is pharmacogenomics?
Branch of pharmacology which deals with the influence of genetic variation on drug response. Allows personalisation of drug treatment.
When is a nuchal scan performed?
Between the 10th and 14th week.
What does a nuchal scan measure and detect?
Thickness of the fluid at the back of the foetus’ head. Increased thickness can indicate chromosomal abnormalities (Down syndrome), birth defects and skeletal dysplasia
What are the two prenatal scanning methods used?
Ultrasound and foetal MRI
When is a foetal MRI performed and what does it measure?
After 20 weeks. Measures nasal bone (another test for Down syndrome and cardiac defects)
When can an ultrasound be performed?
From 5 weeks but best after 9 weeks.
What are the two non-invasive prenatal tests used?
Maternal blood test and cell-free foetal DNA.
How does the maternal blood test work?
Markers in the blood detect an increased risk of foetal trisomy 21, 18 and neural tube defects
How does cell-free foetal DNA work?
Analyses the DNA fragments in the blood. 10-20% of this comes from the placenta which is representative of the unborn foetus.
Which test determines the gender of the baby?
Cell-free foetal DNA
What is cell-free foetal DNA used for?
Determines the sex of the baby and can be used to investigate X-linked recessive disorders.
