A2.3 Viruses + DNA replication (BOOK) Flashcards
For enveloped viruses, what type of cell do they usually infect?
Animal cells
In which reproductive cycle (?) of viruses are lipid envelopes common to?
Lytic cycle (because of lysis)
Describe the bacteriophage lambda on terms of the type of virus
Bacteriophage
- bacterium/arcaheum hosts
Is the bacteriophage lambda enveloped or non-enveloped?
Non-enveloped
What is the genetic material of bacteriophage lambda?
- Double stranded DNA
- both negative and positive strands
-32 genes for 29 proteins
-4 enzymes
Give the distinctive features of the bacteriophage lambda
- lytic cycle OR lysogenic cycle
What is the host of the Bacteriophage Lambda?
e. coli
Give the parts of the bacteriophage lambda.
Describe COVID-19 (Type of Virus)
- coronavirus
- crown-like
- animal cell host
COVID-19 (Enveloped or Non-Enveloped)
Enveloped
COVID-19 (Genetic Material)
- 1 stranded positive sense RNA
- 16 genes: 29 proteins
- 6 enzymes
COVID-19 distinctive features
- Zoonosis
- from a bat
Host of COVID-19
Human cells and other epithelium mammal cells
HIV type of virus
- retrovirus
HIV enveloped or non-enveloped
Enveloped
HIV genetic material
- 2 copies of a single-stranded positive sense RNA
- 9 genes: 15 viral proteins
- 4 enzymes
Host of HIV
T-Helper cells in the human immune system
Give the parts of COVID 19
give the parts of HIV
For the lytic cycle, after lysis, how many viruses pop out?
~100
How many times is the viral DNA replicated in the lytic cycle?
- around 100 times by a rolling circle method
What are the two enzymes in HIV that cause mutations ?
- reverse transcriptase (for retroviruses only)
- cytidine deaminase (general)
Why do mutations happen more often in viruses in regards to enzymes?
- They don’t proofread
Define cytidine deaminase
enzyme that converts cytosine to uracil
Why does HIV have the highest known mutation rate of any virus?
- reverse transcriptase
- cytidine deaminase
Describe the influenza virus
- enveloped
- negative sense RNA
- uses RNA replicase -> high mutation rate
- haemagglutinin protein to bind to a host cell
- neuraminidase to help with release into host cell
What is the rule that one nitrogen base must always pair with the other?
Complementary base pairing
What is the duty of DNA polymerase I?
- exonuclease
- break bonds between nucleotides and polymerase by linking nucleotides
- replaces RNA nucleotides w/ DNA nucleotides
DNA ligase duty
- Seal the nicks left by DNA polymerase I
How many times on a leading strand is the primer added?
- 1 time
How many times are RNA primers added to the lagging strand?
every 100-200 times
In prokaryotes, who proofreads the DNA replication process and how?
- DNA polymerase III
- removes incorrect nucleotide
- moves back 1 nucleotide
- then inserts the CORRECT nucleotide
Describe the procedure of the Messelsohn-Stahl Experiment
- Uses E. Coli which makes DNA molecules from nitrogen compounds in their food
- TRANSFERRED TO 15N -> 14N (old -> new) -> density
- DNA molecules centrifuged
- After first cell division: Mixed density (old + new)
- After second: Mixed density + light density (mixed + just new)
Conclusion of Messelsohn-Stahl
- DNA is semi conservative
Define dispersive
Each individual DNA strand is a “patchwork” of original and new DNA
Describe gel electrophoresis
- separates DNA fragments by length
- gel placed in tank with electrolyte solution
- DNA samples in wells
- negative to positive movement
- larger DNA molecules lesser + opp.
- After, gel is treated with dye to visualize DNA
- Visible bands
- DNA ladder placed in one lane
- DNA bands in other lanes
Outline two potential applications of PCR and gel electrophoresis
- testing for coronaviruses
- DNA profiling for paternity testing
Describe how PCR can be used to test for coronavirus
- swab in nose or throat
- RNA -> DNA BY REVERSE TRANSCRIPTASE
- PCR to amplify specific viral base sequences that are markers
- fluorescent markers are attached to any DNA produced
Give the advantages and disadvantages of using PCR and gel electrophoresis for coronavirus testing
- Advantage: sensitive — 1 molecule of viral DNA -> 35 bil. mol. of DNA
- Advantage: primers can be designed so only 1 viral strain dectected
- Disadvantage: Requires very expensive equipment
- Due to time needed for thermal cycling, no immediate results