Exam 2 Terminology Flashcards
Polymerase Chain Reaction (PCR)
Technique used to make multiple copies of a segment of DNA. It is precise, fast and inexpensive. Result: Two new DNA molecules are obtained from the original one.
3 steps of PCR
- Denaturation
- Annealing
- Extension/Elongation
Denaturation
To amplify a segment of DNA using PCR, the sample is first heated so the DNA denatures, or separates into two pieces of single-stranded DNA.
Annealing
Two short stretches of nucleotides (20-30 nucleotides long), known as primers, attach to ends of each of the two separated DNA segments. Forward primer (+ sense) binds to reverse DNA strand (- sense strand) and vice versa
Extension/Elongation
An enzyme builds two new strands of DNA using the original strands as a template. Thus, a new DNA segment extending from the primer, and complementary to original DNA segment is created.
Taq polymerase
The enzyme used in extension/elongation. It keeps on adding free nucleotides (complementary to the corresponding nucleotides of original DNA segment) to the attached primer.
Real Time PCR
Also known as quantitative PCR. Allows monitoring and quantification of increasing accumulation of PCR product/nucleic acid load as the reaction progresses.
Genome Sequencing
Process by which the sequence of bases in a DNA molecule is elucidated/can be obtained and read.
Next Generation Sequencing (NGS)
Cheaper, quicker, less DNA, has high throughput, and is more accurate and reliable than Sanger sequencing.
Metagenomics
The study of the collective set of microbial population in a sample by analyzing the sample’s entire nucleotide sequence content, and is a powerful method for random detection of existing and new pathogens.
Why does genome sequencing play a crucial role in surveillance studies?
It allows:
- Pathogen detection
- Studies on genetic variation
- Identification of unidentified strains
- Development of diagnostics
- Identifies genes associated with drug resistance
- Judges the efficacy of current vaccine and formualting new vaccine strategies
Phylogenetic Analysis
The use of virus genome sequence data to study evolution of viruses and genetic relationships among viruses.
Microarrays
Shows positive reactions between probe DNA and sample DNA (hybridization). Generates a fluorescent signal from the spot where probe DNA is spotted in the chip.
Advantage of microarrays
Hundreds of pathogens can be screen for simultaneously using a single micoarray chip.
Antiviral Drugs
Interfere with the ability to infiltrate a target cell or target different stages of replication/synthesis of components required for replication of the virus.
Antimicrobial Chemotherapy
The treatment of infectious diseases by drugs (chemical compounds) that are inhibitory or lethal to the pathogenic microbe.
Antibiotics
AKA antibacterials, are types of medications that destroy or slow down the growth of bacteria.
Antimycotics
Medications used to treat fungal diseases.
Antiparasitics
Are a class of medications which are indicated for the treatment of parasitic diseases.
What is the best logical approach of a new antiviral drug?
It will interfere with virus replication without harming or causing minimal harm to the infected host cell.
Antiviral Difficulties
Difficulties encountered in development of broad spectrum antivirals with low cytotoxicity.
How does an antiviral act?
Antivirals can stop the receptor binding, stop uncoating, stop protein nucleic and protein synthesis, stop assembly, and stop release.
Acyclovir
- Activity primarily restricted to herpesviruses
- Is a synthetic nucleoside analog of deoxyguanosine
Acyclovir Treatment of?
Herpesviruses infections in humans, Feline herpesvirus-1 induced corneal ulcers, and Equine herpesvirus-1 induced encaphalomyelitis.
Acyclovir Mechanisms of Antiviral Effect
- Acyclovir molecules entering the cell are converted to acyclovir monophosphate by virus induced thymidine kinase enzyme
- Host cell enzymes add two more phosphates to form acyclovir triphosphate, which is transported to the nucleus
- Cleavage of 2 phosphates from the acyclovir triphosphate by the herpes simplex’s own enzymes to form acyclovir monophosphate
- The herpes simplex’s DNA polymerase enzyme incorporates the acyclovir monophosphate into the growing DNA strand as if it were 2-deoxyguanosine monophosphate (a “G” base)
Stop the growing viral DNA chain
Further elongation of the growing viral DNA chain is impossible because acyclovir monophosphate lacks the attachment point necessary for the insertion of any additional nucleotides.