Microbiology- Chapter 11

The Baltimore classification scheme is a useful way to categorize viruses based on their host infectivity.

false

To date, there is no evidence that RNA viruses infect Archaea.

false

Varied transcription mechanisms distinguish the different DNA virus Baltimore classes, whereas varied translational mechanisms distinguish RNA viruses.

false

Viruses are known to infect Bacteria, but no virus has yet been found that infects Archaea

false

Viruses that contain positive-strands genomes do not share genetic elements with positive-strand genomes

false

The T4 phage protects its DNA from host restriction endonuclease by

glucosylating cytosine bases in the T4 genome to prevent DnA cleavage

Polyproteins made from human viruses such as poliovirus must be ________ in order to yield the required functional units of the virus.

post-translationally cleaved

The genome of retroviruses contains genes to make all of the following EXCEPT

repressor proteins

A drug designed to inhibit reverse transcriptase activity would target

retroviruses

The Baltimore Scheme to classify viruses contain a total of ______ groups based on _____.

seven/ genome composition and transcription mechanism

Herpes viruses can cause all of the following diseases in humans EXCEPT

spongiform encephalopathy

Which feature, if changed, would NOT abolish M13's utility as a cloning vector?

ssDNA genome becoming a dsDNA genome

Proteins made by a ribosome reading through the stop codon of a transcript without their own discrete ribosome binding sites

suggest a relatively low level of protein product is essential for the virus due to the rare frequency of these events

Prophage formation occurs after lambda infection if A) the cI gene is transcribed and cI protein accumulates. B) cII expression occurs. C) Cro accumulates in the cell. D) both Cro and cI are equally activated.

the cI gene is transcribed and cI protein accumulates

In E. coli, the adenine in the sequence GATC is methylated by the Dam enzyme. In the same cells, a restriction endonuclease recognizes and cleaves dsDNA with the sequence GATC on either strand. Why does E. coli have these two enzymes?

the enzymes protects E. coli from infection by preferentially degrading viral or other exogenous DNA that is not methlated

As a consequence of the immune system in humans recognizing dsRNA as foreign

the genomes of dsRNA viruses must avoid human immune cells during infection, including replicating their genomes within their own nucleocapsids.

Early and late viral proteins are classified according to their relative

time of synthesis following host infection

Despite viruses require a living host's metabolism to replicate, it remains unclear whether viruses existed before living cells.

true

Genomics analysis of recently isolated viruses indicate some viruses contain larger genomes than the some bacterial genomes.

true

One hypothesis on the origin of DNA points to RNA viruses evolving a modified nucleotide that is insensitive to ribonucleases

true

The HIV genome consists of

two identical ssRNA molecules.

Spindle-shaped viruses have been shown to infect only

Archaea

Unusually shaped viruses, such as lemon-shaped and spindle-shaped, have recently been discovered in

Archaea

Due to the genetic diversity of viruses and their lack of ribosomal RNA, nucleotide-based phylogeny studies are not applicable to virology

False

In prokaryotes, DNA viruses replicate their genomes in the nucleus while RNA viruses are replicated in the cytoplasm

False

Nonfilamentous bacteriophages often can escape a host without lysing, whereas filamentous phages normally induce cell lysis once replicated inside a host.

False

Viroids infect only fungi

False

Based on its function, which type(s) of viruses likely contain(s) a gene encoding for RNA replicase?

Positive and negative ssRNA viruses

Which type of viruses can be directly used for translation?

Positive ssRNA

Accumulation of the cI protein results in integration of the lambda genome and prophage formation.

True

By nature of its infectivity, M13 phage can be used in the laboratory to continually propagate a particular DNA sequence inside of Escherichia coli by simply culturing infected E. coli in LB.

True

Due to their indispensable role for copying its genome, an intracellular host protease that attacks the adenoviral protein ends would likely result in halting its replication.

True

In order to replicate its genome, a positive-strand RNA virus must produce a complete negative-strand RNA molecule that serves as the template for protein synthesis.

True

Many viruses that infect humans may illicit a strong immune response causing additional harmful effects, so the discovery of a virus that can induce an immune response without causing harm made it attractive for vaccine development.

True

Most archaea viruses identified appear to have DNA genomes

True

Some virus shapes that infect members of Archaea are unique from other viruses that infect eukaryotes and bacteria.

True

Which of the following conditions favors a lysogenic life cycle in bacteriophages?

a lack of host bacteria

Bacteriophages that have single-stranded genomes are specialized to minimize energy requirements because just one strand is necessary for replication.

False

The unconventional dsDNA genome replication mechanism where no lagging strand exists is a hallmark of which group of viruses?

Adenovirus

The hepadnaviral DNA polymerase acts as which of the following?

DNA polymerase, reverse transcriptase, and protein primer for DNA synthesis

How could overlapping genes in a positive ssDNA virus genome be predicted?

Directly search the three frames of the positive ssDNA for genes that have sequences where more than one gene is predicted

A bacteriophage that lacks its proteinaceous capsid structure is also called a viroid

False

An RNA genome itself serves as mRNA in negative-stranded RNA viruses.

False

What is unusual about phage MS2 infection of Escherichia Coli?

It attaches to the host's pilus rather than the cell's surface

If the hypothesis stating viruses evolved prior to living organisms on Earth is true, the first type of viruses in the world were likely

RNA viruses

Which type of viruses generally has the smallest genome?

RNA viruses

Of the phages listed below, which contains a double-stranded DNA genome composed of early and late genes

T7

How are T7 genes transcribed?

T7 has its own RNA polymerase, which must first be synthesized by the host.

You isolate a bacteriophage that can replicate in E. coli. Through chemical analyses you determine that the only nucleic acid present is RNA. You isolate the RNA and put it in a test tube with all of the enzymes, amino acids, and RNAs necessary for translation. The RNA is translated directly, without being copied into a complementary strand first, and new infectious virions are made and released. What does this tell you about the bacteriophage?

The viral genome is ssRNA of the plus sense

How do reoviruses increase the translational activity of human ribosomes so that they can rapidly produce viral proteins during infection? A) They chemically modify the RNA transcripts with methyl caps in a similar manner to normal eukaryotic RNA processing. B) They keep a ribosome binding site specific to human ribosomes on their genome. C) They have introns and sometimes extons in their genomes to make their RNA resemble eukaryotic mRNA. D) They only adhere to and infect metabolically active host cells where protein synthesis is high.

They chemically modify the RNA transcripts with methyl caps in a similar manner to normal eukaryotic RNA processing

What is the purpose of synthesizing a negative strand of RNA in a positive ssRNA virus?

To serve as the complementary template sequence in genome amplification of the positive strand

The _____ has been especially useful for genetic engineering because it is capable of triggering a substantial immune response without causing major adverse health effects.

Vaccinia virus

When two different influenza viruses infect the same cell, their segmented genomes can undergo reassortment which will result in

antigenic shift

The filamentous DNA phages are unusual, because they

are released from the host without the host being lysed

Blocking polyomavirus SV40's ability to integrate its genome into host cells would

avoid cancer development caused by the virus

In T7, the proteins that inhibit the host restriction system are synthesized

before the entire T7 genome enter the cell

Rolling circle replication of the lambda genome differs from replication of a bacterial chromosome in that

bidirectional replication forks are not form

A concatemer is a

combination of two or more repeated nucleotide sequences covalently linked together

The family of reoviruses contain dsRNA genomes use a ________ replication process. A) conservative B) semiconservative C) retroviral D) rolling circle

conservative

Identifying that protease are essential for the replication of a virus would suggest that the virus

contains at least one polyprotein

Among the largest RNA genome viruses are ________ which contain a ________ genome.

coronaviruses/ positive ssRNA

In designing a drug to inhibit pox viruses, the compound should localize in the host's ________ to be MOST effective.

cytoplasm

You are attempting to mutate lambda to affect whether lysis or lysogeny occurs after infection. Which mutation would INCREASE the chances of lysogeny over lysis?

deletion or inactivation of the cro gene

Mu is a(n) _____ virus

dsDNA

Prokaryotic restriction endonucleases are effective at destroying a virus whose genome consists of

dsDNA

Viruses that infect the hyperthermophilic Archaea tend to contain genomes that are composed of

dsDNA

Reoviruses contain ________ genomes, and their replication occurs within the host's ________.

dsRNA/ cytoplasm

In contrast to positive ssRNA viruses such as coronaviruses and polioviruses, the genome of retroviruses

must first integrate into the host's genome before transcription