Biochem Flashcards
What are the 5 levels of gene expression?
- Genome
- Transcription
- RNA processing and nuclear export
- Translation
- Post translation
DNA and protein are complexed together to form what?
Chromatin
Modifications of DNA that switch specific gene expression on/off
Epigenetic mechanisms
What is the fundamental reaction in RNA synthesis?
Formation of phosphodiester bonds
How does RNA synthesis majorly differ from DNA synthesis?
RNA synthesis does not require a primer
What are promotors?
DNA sequences upstream ( in front ) of the coding sequence
What are non-coding RNA’s also known as?
RNA interference RNAi
What does the term “cancer-critical” refer to?
All genes whose alteration contributes to, causing or evolution of, cancer by driving tumour development
The study of how behaviour and environment cause changes affecting the way genes work
Epigenetics
The development of secondary malignant tumour at a distant site from primary cancer origin
Metastasis
What are the two main classes of cancer-critical genes?
- Proto-oncogenes
- Tumour-suppressor Genes
What mutation drives proto-oncogenes towards cancer?
A gain-of-function mutation
Mutant, overactive or over-expressed forms of proto-oncogenes are known as?
Oncogenes
What mutation drives tumour-suppressor genes towards cancer?
Loss of function mutation
Give an example of a tumour suppressor gene
TP53
Define loss of function
Generally refers to the tumour suppressor genes, where loss of function leads towards cancer development
Define gain of function
Generally referees to a situation where gain of function leads towards cancer development. For example, oncogenes.
What three key pathways are often found to be damaged in tumours?
- P53
- Rb
- RTK/Ras/PI3K
What is the role of the p53 pathway?
Genes within the pathway regulate responses to stress and DNA damage
What is the role of the Rb pathway?
Involved in initiation of the cell division cycle
What is the role of the RTK/Ras/PI3K pathway?
Transmits signals for cell growth and division from the outside of the cell into the cell
What type of gene is p53?
Tumour suppressor gene
What gene encodes p53?
TP53
What are the key functions of p53?
- activation can result in cell cycle arrest, loss of cell power/growth and apoptosis
What enzyme targets p53 for degradation?
E3
What is the protein TAG that is attached to proteins, which are targeted for degradation?
Ubiquitin
A rare childhood tumour in the neural precursor cells of the retina?
Retinoblastoma
What type of mutation, on what chromosomes, results in retinoblastoma?
Deletion at specific region of chromosome 13
What is the role of the Rb gene?
Encodes the Rb protein
Define oncogenes
Genes that encode proteins that have the ability to cause cellular transformation
What is the result of this over activity:
- deletion or point mutation in coding sequence
Normal amounts of hyperactive protein
What is the result of this over activity:
- mutation in the regulatory region of the gene
Normal protein overproduced
What is the result of this over activity:
- gene amplification
Normal protein greatly overproduced
What are the results of this over activity:
- chromosome rearrangement
Changes to regulatory region that result in:
normal protein overproduced
OR
alters the protein coding region causing transcribed gene (hyperactive protein)
What is the function of the Ras protein?
Transmit signals from cell surface receptors into the cell
What is the type of mutation associated with Ras oncogenes?
Point mutation
What pathway is critical for cell growth control?
PI3/Akt/mTOR
How can the complete DNA sequence of cancer cell genome be easily obtained?
Exome analysis
What are the two ways that cells communicate with each other?
Electrical or chemical communication
Which type of cell communication is very fast and depends upon the presence of gap junctions for information to pass from one cell to another?
Electrical communication
Which type of cell communication is the major form of information transfer between cells, where one cell releases a stimulus which alters the activity of another cell?
Chemical communication
In order to trigger a response, where must cell signals be transmitted?
Across the cell membrane
Name five types of signalling molecules
- Growth factors
- Hormones
- Extracellular matrix molecules
- Drugs
- Chemicals
Through what mechanism do most receptors relay information in cell signalling?
Phosphorylation
What group of enzymes are responsible for phosphorylation?
Kinases
When cell communication goes wrong, what is the result?
Disease
Give an example of a disease resulting from loss of a signal
Type 1 diabetes- pancreatic cells that produce insulin are lost
Give an example of a disease resulting from an inability for signal to reach target
Multiple sclerosis -protective wrappings around nerve cells in CNS are destroyed, effected nerve cells can no longer transmit signals
Give an example of of a disease resulting from a target ignoring the signal
Type 2 diabetes- cells lose ability to respond to insulin
Give an example of a disease resulting from too much signal being transmitted
Brain damage by excitotoxicity- occurs after stroke due to high concentrations of glutamate being released by dying cells
Give an example of a disease resulting from multiple breakdown of signals
Cancer
What do many disease treatments rely on?
Cell signalling
What are the six hallmarks of cancer?
- Sustaining proliferative signalling
- Evading growth suppressors
- Activating invasion and metastasis
- Enabling replicative immortality
- Inducing angiogenesis
- Resisting cell death
What are the two most common growth factors in oral cancer?
- Epidermal growth factor (EGF)
- Transforming growth factor alpha (TGF- alpha)
Which growth factor is most overexpressed (80-90%) in oral cancer?
Epidermal growth factor (EGF)
What growth factor family plays an important role in angiogenesis?
Vascular endothelial growth factor (VEGF)
What process is absolutely necessary for the proliferation and metastasis of solid tumours?
Angiogenesis
