Question 1

During the cell cycle in an uninfected cell, the cellular protein Rb represses S phase genes by doing which of the following?

Accepted Answer

Rb represses S phase genes by recruiting histone deacetylase to E2F inducible genes, leading to chromatin condensation and transcriptional repression.

Question 2

There are five families of mature transcripts produced from the major late gene of adenovirus.Which of the following is the MAJOR determinant for which family is produced from the primary transcript?

Accepted Answer

The location of the polyadenylation site is the major determinant for which family is produced from the primary transcript. Each family uses a different polyadenylation site, which generates a different mature transcript. The location of the 5' splice site and the 3' splice site determine the specific splicing pattern for each transcript within a family, but do not determine which family is produced. The location of the transcription start site and the start codon determine the initiation of translation, but do not determine which family is produced from the primary transcript.

Question 3

The CR3 region, found on the13S version of the E1A protein, is involved in activation of transcription by binding to which of the following proteins?

Accepted Answer

E

Question 4

Which component of the adenovirus virion binds to the host cell receptor?

Accepted Answer

The knob on the fiber protein of adenovirus is primarily responsible for binding to the host cell receptor, facilitating the virus's attachment to the host cell. Additionally, the penton base, another component of the adenovirus, can also interact with host cell receptors, particularly integrins, aiding in the virus's internalization. Therefore, both components can bind to different receptors on the host cell.

Question 5

What is the function of the VA RNAs produced by adenovirus?

Accepted Answer

The VA RNAs produced by adenovirus act as inhibitors of the interferon-induced protein kinase R (PKR), which is responsible for inhibiting protein synthesis in response to viral infection. By inhibiting PKR, the virus is able to continue translating its own mRNAs and replicating within the host cell without interference from the host's immune response.

Question 6

Binding of histone deacetylases to the promoters of genes leads to activation of transcription from that promoter.

Accepted Answer

Binding of histone deacetylases (HDACs) to the promoters of genes leads to repression of transcription from that promoter, as HDACs remove acetyl groups from histones, causing them to become more compact and less accessible to transcription factors. This creates a repressive chromatin environment that turns down gene expression.

Question 7

What is the structure of the ends of the adenovirus genome when it is released from the virion into the nucleus?

Accepted Answer

The adenovirus genome, when released into the nucleus, has a terminal protein covalently bound to the 5' end. This unique feature is crucial for the virus's replication process.

Question 8

If the E1A gene is transfected into cultured cells, it causes an abortive transformation and the cells die.If the E1B gene is included with E1A, then cells become fully transformed and survive.What critical function does the E1B gene provide?

Accepted Answer

The E1B proteins have been shown to suppress apoptosis, which allows cells to survive and become fully transformed when the E1B gene is included with E1A.

Question 9

Adenovirus virions are transported to the nucleus of the host cell via an interaction between the hexon proteins and which of the following cellular structures?

Accepted Answer

Adenovirus virions are transported to the nucleus of the host cell via an interaction with the microtubules. The hexon proteins on the surface of the virus bind to dynein motors anchored on the microtubules, which then transport the virus to the nucleus. The other choices listed do not play a significant role in the transport of adenovirus to the nucleus.

Question 10

During infection with adenovirus which of the following events activates the production of the major late transcripts?

Accepted Answer

Replication of the viral genome is a key event that activates the production of the major late transcripts in adenovirus infection. This is because the switch to late gene expression, which includes structural proteins necessary for assembling new virus particles, is tightly linked to the replication of the viral DNA.

Question 11

Adenovirus virions are composed of which of the following components?

Accepted Answer

Adenovirus virions are composed of hexons composed of trimers of the hexon protein, penton bases composed of five copies of the penton protein, and penton fibers composed of trimers of polypeptide IV. Additionally, basic polypeptides are bound to the viral DNA. Therefore, all of the above components are correct.

Question 12

All of the following are involved in determining the type of mRNAs produced during adenovirus infection EXCEPT…..

Accepted Answer

The type of mRNAs produced during adenovirus infection is determined by factors such as transcription initiation by RNA polymerase II, the location of transcriptional promoters, alternative mRNA splicing, and alternative polyadenylation sites. The location of the start codons is not directly involved in determining the types of mRNAs produced; it is more related to the translation process and the determination of the starting point for protein synthesis.

Question 13

Which of the following describes the function of the terminal protein in the replication of the genome of adenovirus?

Accepted Answer

The terminal protein serves as the primer for DNA replication in adenovirus genome replication.

Question 14

The proteins produced from which of the following genes from adenovirus serves to suppress apoptosis in infected cells?

Accepted Answer

The protein produced from the E1B gene inhibits apoptosis, allowing infected cells to persist and produce more virus. The other genes listed do not have this function.

Question 15

The tripartite leader found on all of the transcripts produced from the major late gene of adenovirus carries out which of the following functions?

Accepted Answer

The tripartite leader sequence in adenovirus mRNA is known to facilitate ribosome shunting, which helps direct the ribosome to the correct AUG start codon for efficient translation initiation.

Question 16

Which of the following was NOT studied or discovered in adenoviruses?

Accepted Answer

Adenoviruses have been instrumental in the study of mRNA splicing, transcription initiation by RNA polymerase II, and the proteins involved in regulating transcription. They have also been used as vectors in gene therapy. However, the regulation of protein translation has not been a notable area of study or discovery specifically associated with adenoviruses.

Question 17

During DNA replication of the adenovirus genome, the virus only uses continuous synthesis, which means that it does not produce Okazaki fragments.

Accepted Answer

Adenovirus DNA replication involves a protein-primed mechanism that allows continuous synthesis on both strands, eliminating the need for Okazaki fragments typically seen in lagging strand synthesis.

Question 18

The E2 gene encodes all of the following proteins involved in replicating the adenovirus genome EXCEPT:

Accepted Answer

The E2 gene does not encode for ligase, which is involved in the formation of phosphodiester bonds to join adjacent DNA fragments together.

Question 19

The E1A protein from adenovirus indirectly stabilizes the cellular p53 protein.Why is this potentially a problem for the virus?

Accepted Answer

Inducing the apoptosis pathway through stabilization of cellular p53 protein can lead to cell death, which is not favorable for virus replication and spread.

Question 20

The E1A protein from adenovirus can act as an oncogene by inducing tumors in experimental animals.

Accepted Answer

The E1A protein from adenovirus has been shown to induce tumors in experimental animals, making it an oncogene.

Quiz 23: Adenoviruses