SAQs Flashcards
(38 cards)
Describe the function of an effector or target protein in a signalling pathway.
B-Raf is serine/threonine-protein kinase which functions in
the signalling pathway known as the RAS/MAPK pathway
involved in regulation of cell growth and division
What type of mutation commonly occurs in the BRAF gene in
cancer?
Usually point mutations that result in the protein becoming
insensitive to regulatory signals. V600E BRAF mutation
What is the effect of the V600E BRAF mutation on cellular signalling?
BRAF mutants stop responding to signals and leads to constant activation of the downstream pathway
What drugs correct the effects of the BRAF mutation? And how?
Vemurafenib and dabrafenib binds to the active site of the kinase and prevent ATP binding
Describe haw Casgevy works as a gene therapy
- USes CRISPR/Cas 9 gene editing to modify patient’s own haemapoetic Stem cells.
- They then re-express foetal haemoglobin (Hbf) which bypasses the defective adult beta globin chains.
- They are then re-infused which can act as a cure
Describe role of CRISPR/cas 9 system in casgevy therapy.
- it introduces a DNA double strand break at GATA-1 binding site in the BCL11A enhancer region.
- This Prevents GATA1 activating BCL11A expresion
- So allows Gamma globin to be produced which improves the haem function
What is the difference between beta thalassemia and sickle cell disease?
B-thalaseemia
Quantitative
Reduced b-globin so has a low HbA amount
Patient has ineffective haematopoesis which fails to produce red blood cell
Sickle cell
Qualitative
Normal b-globin
HbS is produced instead of HbA
Patient experiences vaso-occlusive crisis
How do you prep patients for casgevy?
They undergo aphoresis to collect the CD34+ haemopoetic stem cells
What is ‘loss of heterozygosity,’?
- Occurs when a cell loses the normal (wild-type) allele of a gene,
leaving only the mutated (defective) allele. - This phenomenon is crucial in TSG inactivation, leading to
uncontrolled cell growth and tumour progression.
How does loss of heterozygosity relate to tumour suppressor genes?
- Most TSGs require both alleles to
be inactivated for cancer development. - In hereditary cancers, an individual inherits one mutated allele but still has one functional allele.
- LOH occurs when the second allele is lost or inactivated leading to complete loss of function of the tumour suppressor
gene. - This concept is the foundation of Knudson’s Two-Hit Hypothesis
Explain how oncogenes contribute to cancer progression
they promote uncontrolled cell division and cell survival
- an example IS KRAS
- It can lead to constant activation of signaling pathways which enhances cell survival.
Describe one role of tumour suppressor genes and provide on example.
- Role = regulate cell cycle and prevent uncontrolled cell growth
Example = TP53 which encodes for the protein p53 which stops the cell cycle If DNA Is damaged
Name two hereditary cancer syndromes and the associated genes.
familial adenomatous polyposis
- which is a mutation in APC gene
Lynch syndrome
- which is a mutation in the DNA mismatch repair genes - ML H1, MSH2, MSH6, EPCAM
Describe the typical cardiovascular phenotypes associated with CHARGE
Syndrome (2 marks)
outflow tract defects incl persistent ductus arteriosus (PDA)
- Septal defects: , atrioventricular septal defect (AVSD), and
ventriculoseptal defects
- Aortic arch anomalies
Epigenetic regulators are one class of genes commonly associated with
congenital heart disease. Name the chromatin remodelling gene
mutated in CHARGE syndrome (1mark)
CHD7
What is chromatin remodelling? (3 marks)
When the Structure of Chroman is altered to regulate DNA acceasibility for transcription, replication or repair
- Chromatin is made of DNA wrapped around histone forming a ‘beads on a string’ structure caued nucleosomes
- chromatin remodelers
use ATP to reposition nucleosomes, converting tightly Packed heterochromatin into loosely packed euchromatin making genes more or less accessible to transcription machinery
Discuss one benefit, and one risk, of CRISPR-Cas9 therapy for a named
haemoglobinopathy in comparison to conventional treatment
A benefit for beta thalassemia patients is patients might become
transfusion independent, so there is no risk of iron overload or no
requirement for iron chelating therapy, no risk of transfusion
reactions, or no difficulties finding matched transfusion products.
- A risk is that it may not work. It is a very intensive treatment
protocol and if it doesn’t work the patient is right back where they
started. We also don’t know about the long term effects of gene
editing therapies as we do for more conventional options
How is the CTFR gene regulated?
- PKA phosphorylates the R domain
- Nucleotide Binding Domians binds and hydrolyses ATP
- When the channel Opens, Cl-
(chloride ions) moves with
concentration gradient - CFTR is unique in that it also regulates the activity of other
channels incl
What is x-linked inactivation?
When one of two X Chromosomes in female is randomly silenced to equalise gene expression
And ensure dosage compensation.
Explain the role of Xist LncRNA in process of X inactivation
Expressed by inactivated X chromosomes,
It coats the X chromosome in cis
It then recruits silencing complexes
How do lncRNAs control gene expression?
Transcriptionally –
- so through DNA-Chromatin interactions
- So they can inhibit Pol II by binding to that region using
complementary binding and act as a antisense so they inhibit the
actual transcription reaction
- or
- they can interact with proteins and recruit chromatin-modifying
complexes to shut down the expression
Post-transcriptionally (RNA-Cytoplasm) -
- It can directly affect the RNA translation
- Or it can affect the RNA stability meaning it never gets translated it
just gets degraded
How are CD3+ cell numbers increased prior to genetic modifications
-expanded in vitro through activation and stimulation
T-cells are isolated and activated using agents that mimic APC signals through engagement of T-cel receptors
- this activation causes T-cells to proliferate rapidly
What method is used to activate CD3+ T-cells during
CAR T-Cell manufactung.
magnetic beads coated with anti-CD3 and anti-CD28.
How is Alzheimer’s caused
It is a multifactorial disease
-caused by the abnormal amounts ot Ameloid beta which accumulates as plaque and Tau proteins
