Retroviridae Part I Flashcards
The following are properties of Retroviruses EXCEPT:
A. Oncogenic B. Cause immune-suppression C. Cause immune-mediated disease D. Can be endogenous in host cell germ line E. Posses double-stranded RNA
E.
They are SINGLE-STRANDED, but posses TWO molecules of DNA, and are thus DIPLOID
(I believe this diploid genome is unique for the RNA viruses we have learned)
Which of the following is MISMATCHED for Retroviral genes and their products?
A. gag: capsid, matrix, and nucleoproteins
B. pol: reverse transcriptase and integrase
C. env: surface and transmembrane
D. gag: virion core proteins
E. All of the above are correct
E.
T/F:
The defective Retroviruses possess gag, pol, and env genes.
False.
NON-defective
Which of the following is NOT correct about Reverse Transcriptase?
A. RNA-dependent DNA polymerase B. Possessed by all Retroviruses C. RNA genomes are converted to a DNA intermediate, known as the provirus D. It acts in the nucleus E. C and E
E.
It is just the DNA intermediate, cDNA (copy of DNA) when RT is done with it. It is not the provirus until it is INTEGRATED into the host cell DNA
RT acts in the cytoplasm, then the viral DNA goes into the nucleus and gets acted on by Integrase
T/F:
Something unique about the structure of Retroviruses is that they have an icosahedral capsid, with the innermost genome-nucleocapsid complex is helical shaped.
True
T/F:
Reverse Transcriptase has a faulty 3’-5’ proofreading mechanism, resulting in a high rate of mutations in Retroviruses.
True
Which of the following is NOT correct for Endogenouse Retroviruses?
A. Also known as Retroelements
B. Stretches of DNA in the genome of most vertebrates that resemble Retroviruses
C. Presumed to be vestiges of Retroviral integration into the genome throughout evolution.
D. Could be reactivated during periods of immunosuppression
E. Transmitted only as provirus into germ cells, and thus will remain silent and non-pathogenic
D.
They are silent and non-pathogenic;
No evidence of them ever causing disease
The following are true of acutely-transforming Retroviruses, EXCEPT:
A. Directly oncogenic via possession of additional viral oncogene, v-onc
B. When virus accepts c-onc, it loses its viral env gene
C. Gains v-onc when c-onc inserted into virus genome and recombines with host DNA
D. They are non-defective viruses
D.
Most are replication-defective, and need non-defective viruses to replicate, with a few exceptions.
T/F:
Acutely-transforming Retroviruses, by virtue of them having lost the env gene in their attainment of v-onc, cannot synthesize an envelope, are replication defective, and thus must associate with non-defective viruses to replicate.
True
T/F:
Rous-Sarcoma is an acutely-transforming v-onc containing virus, thus it cannot synthesize a complete envelope or replicate on its own without a non-defective viruse.
False!
This was given as the exception- this virus has v-onc but can replicate on its own.
T/F:
Slow/Chronic transforming Retroviruses cause cancer by inserting their viral genes into the host genome at special promoter or enhancer sites that increase the expression of c-onc (proto-oncogene), leading to malignant transformation of the host cell. They do NOT, however, have v-onc!
True
Which of the following is NOT true of Enzootic Bovine Leukosis?
A. Also known as Bovine Leukemia
B. It is associated with B-lymphocytes, especially those that express IgM
C. The pX protein contributes to induction of leukemia and lymphoma
D. It is a member of Deltaretrovirus genus and subfamily Orthoretrovirinae
E. All of the above are true
C. Is not correct
The pX gene codes for Tax protein, which plays a central role in development of leukemia and also lymphoma
I think Deltavirus because cows produce milk and there is a lot of Vit. D in milk; all of the retro’s we cover in class are in the subfamily Orthoretrovirinae.
The following are correct for the pX protein of Deltaretrovirus EXCEPT:
A. Unique sequence situated between the env gene and the 3’LTR
B. It is of viral origin, and is an oncogene
C. It encodes the regulatory Tax protein
D. Unique sequence that sits just before the env gene and the 3’LTR
E. Only D is incorrect
F. B and D are incorrect
F. B and D incorrect
pX IS of viral origin, so thus it is NOT an oncogene. If it were of host cell origin, it could be an oncogene
It is located between env and 3’ LTR
How I remember it is…before cows start p90X, they are envious, then they do p90X, then LATER they are a size 3!
What are two modes of transmission that are important for Enzootic Bovine Leukosis?
A. Ingestion of contaminated food/water, contaminated teat milking cups
B. Blood transfusions, contaminated teat milking cups
C. Blood transfusions, venereal transmission
D. Blood transfusions, contaminated rectal palpation sleeves.
D. Blood blood blood!
T/F:
Resistance to Enzootic Bovine Leukosis is related to genetic differences in Class II MHC genes, termed BoLa (Bovine Leukocyte Antigen); BoLa Aw-7 alleles are susceptible, whereas BoLa aw-12 cows are resistant.
False!
BoLa-12= susceptible BoLa-7= resistant
The only way I can think of to remember this is “Bola is an odd cow (7 is an odd #); she is the odd one of the group, so she is resistant to peer pressure.”
Which is CORRECT for Enzootic Bovine Leukosis stages of disease?
A. Primary infection lasts a few weeks, and is when provirus is expressed in virions and begins to infect B-cells; you may see flu-like signs
B. Persistent infection lasts months or even years, and is when the animals become latent carriers.
C. Persistent lymphocytosis phase follows persistent infection phase and is when virus causes benign proliferation of B-cells, and lasts years. Affects 30-70% of infected cows.
D. Tumor phase affects 5-10% of infected cows, and is when B-cells transform into lymphoma; sudden death can be seen.
E. All of the above.
E.
The tumor phase of Enzootic Bovine Leukosis is defined by all of the following EXCEPT:
A. Generally occurs after the lymphocytosis phase
B. Animals develop malignant lymphoma during this phase
C. Hemorrhage of the spleen can result in sudden death.
D. You can see lymphoma even if the animal has not gone through the persistent lymphocytosis phase.
E. This will occur in 30-70% of infected cows.
E.
TUMOR PHASE=5-10% of infected cattle
