Lecture 5 - Molecular Diagnostics Flashcards
What are molecular diagnostics?
Various molecular biology techniques used to analyze biological markers in the genome and proteome
What are molecular diagnostics used for?
- Monitoring disease
- Detecting disease risk
- Identify therapies
Pharmacogenomics
Using molecular biology technologies to predict a response to drugs (differences in enzymes involved in metabolism)
How are molecular diagnostics used in infectious disease?
- Identify infection status
- Identify strains
How are molecular diagnostics used in cancer?
- Breast cancer risk (BRCA1/2)
- Diagnostics
- Oncogene mutations
Which factors are leading to the growth of molecular diagnostic techniques?
- Zoonotic diseases
- Animal agriculture
- Pet adoption and healthcare
- Pet insurance
Molecular diagnostic techniques for DNA/RNA
- Sanger sequencing
- SNP microarrays
- Next-generation sequencing
- PCR
- Isothermal amplification
Molecular diagnostic techniques for proteins
- ELISA (enzyme-linked immunosorbent assay)
- Proteomics
PCR is used to
- Amplify target DNA and RNA
- Test for the presence or quantity of DNA/RNA in a sample
- Targeted genotyping (single SNPs or insertion/mutation)
- Facilitate other applications such as sanger sequencing or DNA metabarcoding (by amplifying DNA)
What is needed for PCR?
- A DNA template
- A pair of synthetic single stranded DNA primers
- dNTPs (deoxyribonucleotide triphosphates)
- A heat stable polymerase (Taq)
Taq polymerase
A heat-stable polymerase from the bacteria Thermus aquaticus
Downsides of Taq polymerase
Unable to repair base pair errors during replication (cannot proofread)
The amount of DNA ____ every cycle of PCR
Doubles
How can molecular diagnostics determine disease risk?
Looks at the presence/absence of SNPs that cause disease
What is the role of the heat-stable polymerase in PCR?
To extend the primer
Binding requirements for PCR primer design
Must only bind at one location on the genome
Length requirements for PCR primer
18-25 nucleotides, helps avoid having a similar sequence elsewhere that the primer could bind to
Melting temperature requirements for PCR primer design
The temperature at which the pair of primers dissociate from the template should be within +/-5 degrees celcius
Primer dimers
When forward and backward primers bind together - must be avoided since the primer won’t work if it can bind with itself
Structure requirements for PCR primer design
Structure must be avoided
(idk what this means tbh but its in the slides so if anyone else knows let me know - Aimee)
What allows the visualization of PCR results
Gel electrophoresis
How does gel electrophoresis work?
- Separates DNA molecules by length (smaller molecules travel faster)
- DNA is loaded onto agarose gel and will result in bands at different locations which indicates where different nucleotides are located in the strand
Why is a negative control used in PCR
Contamination is an issue in PCR, a negative control ensures that the sample was not contaminated
What is capillary electrophoresis?
Capillary electrophoresis involves separating segments based on size, similar to gel electrophoresis. This can occur in the same machine as sequencing (ex. Sanger sequencing).