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BIOL 2051 : Viruses Study Guide

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azuremammoth471
15 Mar 2019
School
LSU
Department
Biological Sciences
Course
BIOL 2051
Professor
All

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Document Summary

It has no translational apparatus like all known viruses but does encode several trnas. Early and middle proteins are primarily those needed for dna replication and transcription. Late proteins are the head and tail proteins and enzymes like t4 lysozyme needed for lysis to free the mature phage. ~100 t4 phage are released per infected cell. Translation of the phage proteins requires modifying the host rna polymerase to recognize phage promoters and using the host sigma factor. T4 shuts down host transcription with a phage-encoded anti-sigma factor that binds to the host sigma factor. However, if the cro repressor wins the race it blocks expression of the ci gene before enough ci repressor has been synthesized to switch the early genes off. Will ci or cro protein concentration be higher: the host cell should be dormant (so prophage can survive). Which animal virus is similar to a temperate bacteriophage: lytic destruction of host cells (ex.

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Related Questions

2.)

a.) Are viruses that infect Archaea different from other bacterial viruses?

Yes, they do not have protein coats because of the extreme conditions where they live.
No, they consist of nucleic acid and protein just like other bacterial viruses.
Yes, the structure of archaeal viruses is always completely different from other bacterial viruses.

Yes, they have only DNA genomes.

b.) Of the following examples, which is not a common part of many viral life cycles?

The pox virus genome is replicated by DNA polymerase.
Adenoviruses attach to the cell and the nucleocapsid is taken up by the cell.
Pox viruses replicate in the cytoplasm of the cell.

Once an adenovirus virion is inside a cell, host RNA polymerases transcribe early genes

c.) Some viruses are associated with cancer. There are a variety of ways in which viruses may affect a cell in a way that may lead to cancer. Based on your knowledge of the life cycles of viruses and of molecular genetics, what is one way that this might happen?

Viral genetic material inserts into a host genome close to the termination sequence, far downstream of the promoter, and causes a silent mutation.
Viral genetic material inserts into a host genome in a repetitive noncoding region.
Viral genetic material inserts into a host genome, placing a promoter in a new location and turning on a gene that had previously been turned off.
Viral genetic material inserts into a host genome and causes a mutation in a promoter, turning off a gene that had previously been turned on.

d.) Which statement describes the difference between the normal neuron protein PrPC and the pathogenic version PrPSc?

PrPC is just a protein and the PrPSc is a protein with nucleic acid inside.
The PrPC protein contains more beta sheets while the PrPSc protein contains more alpha helices.
The three-dimensional conformation is identical, but the amino acid sequence is different.
The amino acid sequence is identical, but the three-dimensional conformation is different.

1. A mutation in the gene encoding the integrase enzyme rendersthe protein non-functional. How would the affect the HIV infectioncycle?

Formation of the provirus would bestopped.
Reverse transcription would nolonger be possible.
The gp120 glycoprotein would nolonger be able to bind to the CCR5 receptor.

Cutting and assembling the capsid would be halted.

2. If the viral gene is AUGCCCAGG and the mRNA used to make theviral protein is UACGGGUCC, then the virus is a :

Negative strand RNA virus
Double stranded DNA virus
Retrovirus

Positive strand RNA virus

3. Would treating prions with enzymes that digest nucleotides bean effective neutralization method?

No, prions lack amino acids.
Yes, prion nucleic acids would besusceptible to enzymatic digestion.
No, prions lack phosphodiesterbonds and would not be subject to digestion by these types ofenzymes.

Yes, the bonds between the amino acids would be hydrolyzed.

4. Most Americans born before 1970 have a permanent scar ontheir shoulders from the smallpox vaccine. Why don't youngerAmericans have one?

Smallpox has been eradicated by aworldwide vaccination program.
Smallpox is no longer lethal.
A safer less damaging vaccine wasdeveloped in the early 1970's.

The vaccine is no longer effective due to antigenic shift.

5. What kind of pathogen would retain its ability to causeinfections after being treated with powerful proteolytic chemicalsthat would destroy all proteinaceous material?

A virus
A bacterium
A prion
A fungus

A viroid

6. Select all of the false statements concerning AIDS.

AIDS kills the patient.
Patients die as a result ofopportunistic infections.
AIDS shuts down the immunesystem.
HIV therapy (HAART) can clear thevirus from the bloodstream.

HIV therapy (HAART) can clear the virus from the patient'sbody.

7. Why do viruses only infect specific types of cells?

Viruses only attack epithelialcells, such as the cells lining the lungs.
If a host cell is weakened, viruseshave an easier time infecting it.
The initial choice is random butonce a cell type is chosen it becomes the preferred host.
The host cells have the correctsurface receptor that the virus can fit into.

Viruses infect the first cells they encounter.

8. Nucleotide analogs are a class of drugs that are highlyeffective against many types of viruses. They work by halting thereplication of viral genes. They are equally effective at stoppingthe spread of prion diseases.

True

False

9. An experimental chemical has been shown to selectively cleavephosphodiester bonds. How would the affect a virus?

Dissociate the envelope
Fragment the genome
Hydrolyze the protein coating
Alter the host binding site

Digest the capsid

10. HIV uses cell surface receptors to enter host cells. Whydoes switching from a CCR5 co-receptor to a CXCR4 co-receptoreventually shut down the immune system?

Macrophages have CCR5co-receptors.
T-helper cells have CXCR4co-receptors.
T-helper cells are not involved incoordinating immune responses.
Only macrophages are killed byHIV.