Question 1

Bacteriophage T4 blocks transcription of host genes using an enzyme that transfers an ______ from NAD onto the alpha subunit of RNA polymerase.

Accepted Answer

ADP ADP-ribose ADP-ribosyl

Question 2

Attachment of a bacteriophage to its host requires

Accepted Answer

The attachment of bacteriophage to its host requires specific surface proteins on the bacteriophage and specific receptor molecules on the host cell. The interaction between these two molecules is highly specific and facilitates the process of viral entry into the host cell.

Question 3

Late mRNA products in T4 phage include

Accepted Answer

Late mRNA products in T4 phage include phage structural proteins, proteins that help with phage assembly without becoming part of the virion, and proteins involved in cell lysis and phage release. Therefore, all of the above are correct.

Question 4

________ mRNA is synthesized before replication of the viral nucleic acid.

Accepted Answer

The answer of ________ mRNA is synthesized before replication of...

Question 5

_____________ is / are able to degrade infecting bacteriophage DNA,thus protecting the host cell.

Accepted Answer

Restriction endonucleases are enzymes that recognize and cut DNA at specific target sequences, often called restriction sites. When a bacteriophage infects a bacterial cell, its DNA can be identified as foreign and attacked by the restriction endonucleases, which cleave the viral genome into smaller pieces and make it unable to replicate. This is part of a defense mechanism called the restriction-modification system, which helps protect the bacterial cell from being overrun by phages.

Question 6

Phage T4 protects its DNA from cleavage by host restriction enzymes by

Accepted Answer

Phage T4 protects its DNA from host restriction enzymes by substituting glucosylated hydroxymethylcytosine for cytosine, which makes its DNA resistant to cleavage by these enzymes.

Question 7

The tails of some bacteriophage

Accepted Answer

The tails of bacteriophages typically include a tail sheath that contracts, like a syringe, to inject the phage genome into the cytoplasm of the host cell. This contraction is often triggered by receptor binding and triggers the release of the genome into the host. The tails do not rotate or exhibit oar-like motion.

Question 8

For most T4 phages,the nucleic acid enters the host cell but the capsid is left outside.

Accepted Answer

This is true for most T4 phages. The nucleic acid, which is DNA, enters the host cell while the capsid remains outside. The capsid is then degraded.

Question 9

Using the ICTV taxonomy system,a virus name ending in "viridae" would be part of which grouping?

Accepted Answer

A virus name ending in "viridae" represents a virus family in the ICTV taxonomy system.

Question 10

Due to the diversity of retroviruses,they can be placed into more than one Baltimore system group.

Accepted Answer

Retroviruses are specifically classified into Group VI in the Baltimore classification system because they all share the characteristic of reverse transcription.

Question 11

If a single stranded RNA virus contains genomic RNA that is identical to the mRNA that it produces,what type of virus is this categorized as?

Accepted Answer

A single stranded RNA virus containing genomic RNA that is identical to the mRNA that it produces is categorized as either Plus Strand or Positive Strand. Both terms are used interchangeably to describe such viruses.

Question 12

A _____________ is a sequence-specific recognition protein with endonuclease activity.

Accepted Answer

Restriction endonucleases are proteins that recognize and cleave specific DNA sequences. They are commonly used in molecular biology to cut DNA at precise locations for various applications. DNA helicase unwinds double-stranded DNA, terminal transferase adds nucleotides to the ends of DNA strands, and DNA ligase joins two DNA strands together.

Question 13

In T4 phages,which of the following makes the initial contact with the appropriate receptor site?

Accepted Answer

The tail fiber of T4 phages is responsible for making the initial contact with the appropriate receptor site on the host cell. This interaction activates the injection process, which allows the phage DNA to enter the host cell and initiate the infection process. The base plate, collar, and tail tube are all important components of the phage tail, but they do not make direct contact with the host cell receptor site.

Question 14

If a single stranded RNA virus contains genomic RNA that is complementary to the mRNA that it produces,what type of virus is this categorized as?

Accepted Answer

The virus is categorized as a negative strand or minus strand RNA virus. This is because the viral genomic RNA is complementary to the mRNA it produces, meaning it needs to first produce a positive strand mRNA through transcription before it can be translated into proteins by the host cell machinery.

Question 15

Bacteriophage that only exhibit lytic replication cycles are called __________ phages.

Accepted Answer

Virulent phages only undergo the lytic cycle, in which the host cell is lysed and the newly replicated phages are released to infect other host cells. Temperate phages can undergo either the lytic or lysogenic cycle, and intemperate phages are a type of temperate phage that always undergo the lytic cycle. Lytigate is not a term used to describe types of phages.

Question 16

The sequence of genes in each T4 virus within a population is the same but starts with a different gene at the 5' end.If each of these linear pieces is circularized,the gene sequences would be identical.The T4 DNA,therefore,is described as being

Accepted Answer

The fact that each T4 virus within a population has the same sequence of genes but starts with a different gene at the 5' end suggests that the DNA is circularly permuted. This means that the genome can be circularized in different ways without changing the gene sequence. The other answer choices, such as two-fold rotational symmetry or linear palindromes, do not accurately describe this phenomenon.

Question 17

Rubulavirus falls under which group of the ICTV nomenclature system?

Accepted Answer

Rubulavirus is a genus of the Paramyxoviridae family under the order Mononegavirales. Therefore, it falls under the genus category in the ICTV nomenclature system.

Question 18

__________ is an unusual base found in the DNA of T4 phages.

Accepted Answer

The answer of __________ is an unusual base found in...

Question 19

Glucosylation of hydroxymethylcytosine residues protects phage T4 DNA from cleavage by bacterial restriction enzymes.

Accepted Answer

Glucosylation of hydroxymethylcytosine residues in phage T4 DNA prevents the DNA from being cleaved by bacterial restriction enzymes. This modification protects the phage DNA from being degraded by the host bacterial cell.

Question 20

A reverse transcribing DNA virus that wants to replicate its genome must first convert the dsDNA to _______ before using that to create copies of the dsDNA genome.

Accepted Answer

A reverse transcribing DNA virus first converts its dsDNA into single-strand RNA (ssRNA) before using that as a template to synthesize new dsDNA copies.

Quiz 27: Viruses