lecture 14 Flashcards
Retroviruses use which of the following cellular molecules as the primer for genome replication?
A specific transfer RNA.
The 5S ribosomal RNA.
The TATA-box binding protein.
A spliceosome snRNA.
A specific spliceosome protein.
A specific transfer RNA.
All of the following features are associated with the incoming RNA genomes of retroviruses EXCEPT:
3’ poly(A) tails
5’ cap structures.
Repeated (R) sequence at each end of the genome.
A single open reading frame.
Unique sequences at each end of the genome.
A single open reading frame.
Which of the following describes the first step in the replication cycle of retroviruses?
Replication of the host genome into daughter DNA molecules.
Reverse transcription of the viral genome into dsDNA.
Translation of the viral genome into protein.
Transcription of the viral genome into mRNA.
Integration of the viral genome into the host cell DNA.
Reverse transcription of the viral genome into dsDNA.
What is the enzymatic function of the RNaseH activity of reverse transcriptase?
It degrades RNA in an RNA:RNA hybrid.
It converts RNA sequence to DNA sequence.
It degrades RNA in an RNA:DNA hybrid.
It converts RNA sequence to RNA sequence.
It degrades single-stranded RNA.
It degrades RNA in an RNA:DNA hybrid.
All of the following are distinct features of the reverse transcription process, used by retroviruses to convert their ssRNA genome into a dsDNA provirus, EXCEPT…
Degradation of segments of the viral RNA, when bound to a complementary strand of DNA, is important for the process.
There are two separate strand transfer events where the nascent DNA strand is moved to the other end of the template.
A significant number of cellular enzymes are required to carry out reverse transcription.
The R sequence present at both ends of the viral genome is critical in the reverse transcription process.
The viral reverse transcriptase uses a cellular tRNA molecule as a primer.
A significant number of cellular enzymes are required to carry out reverse transcription.
Most retroviruses, with the exception of lentiviruses, can only infect cells that are actively dividing. Which of the following explains the primary reason for this?
The viral genome is amplified by replicating cells.
They need the cell to produce high levels of nucleotide triphosphates.
They need actively replicating cells to spread the virus throughout the body.
They need the cell to undergo mitosis so the viral genome can enter the nucleus.
They need the cell to produce DNA polymerase to replicate the viral genome.
They need the cell to undergo mitosis so the viral genome can enter the nucleus.
Which of the following statements about the integration of the retrovirus provirus into the host genome is FALSE?
During integration, two bases are lost from each end of the viral provirus.
Cellular host DNA repair enzymes are involved in the integration process.
Integration results in a 4-6bp direct repeat of the host cell DNA on either side of the provirus.
Retroviruses produce an enzyme that can remove the provirus from the cellular genome.
The viral integrase makes a staggered cut in the host cell DNA at the site of integration.
Retroviruses produce an enzyme that can remove the provirus from the cellular genome.
Which of the following describes the phenomenon of promoter occlusion seen in retroviruses?
The inability of the LTR to be transcribed because it has integrated into heterochromatin in the host cell genome.
Deletion of the left-hand LTR inhibits transcription from the right-hand LTR.
Transcription from both LTRs can occur simultaneously.
Cellular RNA polymerase can only recognize the factors bound to the left-hand LTR.
Transcription from the left-hand LTR inhibits transcription from the right-hand LTR.
Transcription from the left-hand LTR inhibits transcription from the right-hand LTR.
HIV-1 is a member of which of the following subgroups of retroviruses?
Lentiviruses
Acute transforming retroviruses
Alpharetroviruses
Nontransforming retroviruses
Lentiviruses
Which of the following viruses was thought to have been transmitted to humans and became the source of the HIV-1 pandemic?
African Green monkey SIV
Sooty-mangaby SIV
Chimpanzee SIV
Equine infectious anemia virus
Feline immunodeficiency virus
Chimpanzee SIV
Which of the following is the primary host cell receptor for most of the cell types infected with HIV?
CCR5
DC-SIGN
CD8
CD4
CXCR4
CD4
HIV, unlike most other retroviruses, can infect nondividing cells. Which of the following explains why?
The HIV Vpr protein can direct the nuclear import of the HIV preintegration complex.
All are correct.
The HIV Vpu protein can interact with cellular microtubules to bring the virion close to the nucleus.
The HIV reverse transcriptase enzyme can function with a lower concentration of nucleotide triphosophates.
The HIV integrase enzyme can work without the help of cellular enzymes.
The HIV Vpr protein can direct the nuclear import of the HIV preintegration complex.
What is unusual about how the tat protein from HIV activates transcription from the LTR?
It binds to the reverse transcriptase enzyme and enhances its processivity.
It binds to the tat response element as RNA but not as DNA.
It binds next to the TATA box and enhances binding of TBP to the LTR.
It binds directly to the cellular RNA polymerase II.
It inactivates the repressor of NF-kB so that this protein can bind to the LTR.
It binds to the tat response element as RNA but not as DNA.
The doubly splice mRNAs produced by HIV do not contain the Rev Response Element (RRE). Which of the following explains why they are transported out of the nucleus without the help of the Rev protein?
The HIV Rev protein is still required for their export, but it binds to the poly(A) tail instead of the RRE.
The inportin protein binds directly to the mRNAs to transport them.
They interact with the small subunit of the ribosome, which transport them out of the nucleus
The exportin protein binds directly to the mRNAs to transport them.
They lack the cis-acting repressive sequences.
They lack the cis-acting repressive sequences.
Which of the following describes the function of the HIV protein Vif (viral infectivity factor).
It causes the cellular protein APOBEC3G to be degraded in infected cells.
It allows the unspliced viral genomic RNA to be transported out of the nucleus.
It enhances the packaging of viral genomes into new virions.
It increases the levels of the gp120/gp41 proteins on the surface of infected cells.
It enhances the synthesis of unspliced viral RNA genomes by the cellular RNA polymerase II.
It causes the cellular protein APOBEC3G to be degraded in infected cells.
