Deck 31: Viroids and Hepatitis Delta Virus

Question 1

The RNA polymerase that copies the genome of the avocado sunblotch viroid is highly sensitive to the toxin $\alpha$ -amanitin.

Answer 1

False

Question 2

Which of the following describes the function of the large delta antigen,produced by hepatitis delta virus?

A)It stimulates the binding of the host cell RNA polymerase for genome replication.
B)It carries out the cleavage of the genome multimers into monomers.
C)It is required to package the genome into the hepatitis B virions.
D)It forms capsids to package the hepatitis delta virus genome.
E)It ligates the ends of the RNA genomes together.

Answer 2

C

Question 3

The ribozyme function found in virioids and hepatitis delta virus can be used to cleave exogenous RNA molecules.Which of the following is a requirement for the ribozyme to be recycled and cleave more than one substrate?

A)The entire length of the substrate must not be too long.
B)The structure of the ribozyme RNA must be very stable.
C)Only a short region of complementarity between the target and the ribozyme.
D)The level of magnesium ions must be low enough.
E)The temperature of the reaction must be high enough.

Answer 3

C

Question 4

How is the 3' end of the hepatitis delta virus mRNA formed?

A)It is cleaved by the viral ribozyme activity.
B)It is cleaved and polyadenylated by cellular enzymes.
C)It folds into a distinct stem-loop structure.
D)The polymerase stutters at a poly(U)region in the genome.
E)The delta antigen is covalently attached to the 3' end.

Question 5

Which of the following statements about the plant satellite RNAs is FALSE?

A)Satellite RNAs encode their own capsid protein.
B)Satellite RNAs are transmitted to new hosts via a virion.
C)Satellite RNAs require a helper virus in order to be replicated.
D)Satellite RNA genomes are composed of small circular RNA molecules that contain a high degree of base pairing.
E)Satellite RNAs contain a ribozyme function that can cleave longer RNA molecules into single genomes.

Question 6

The formation of the antigenome template of hepatitis delta virus requires which of the following cellular enzymes?

A)DNA polymerase
B)RNA-dependent RNA polymerase
C)RNA polymerase I
D)RNA polymerase II
E)RNA polymerase III

Question 7

Which of the following mechanisms is used to produce the two different forms of the delta antigen from the hepatitis delta virus?

A)RNA editing by the insertion of an extra base into the mRNA.
B)RNA editing by deamination of a specific base in the genome.
C)Alternative mRNA splicing.
D)Translational readthrough of a stop codon.
E)Ribosomal frameshifting.

Question 8

What is surprising about the observation that a cellular RNA polymerase copies the viroid genome?

A)RNA polymerases usually require a pre-existing RNA primer.
B)RNA polymerases usually transcribe from a DNA template.
C)RNA polymerases don't usually synthesize DNA.
D)RNA polymerases don't usually initiate synthesis from a protein primer.
E)RNA polymerases are not found in the cytoplasm of the host cell.

Question 9

Which of the following groups of organisms do viroids cause disease in?

A)Plants
B)Insects
C)Mammals
D)Algae
E)Paramecia

Question 10

The deamination of an adenine residue in the genome of the hepatitis delta virus causes which of the following to occur?

A)A stop codon to be converted to a tryptophan codon.
B)A stop codon to be converted to a start codon.
C)A 5' splicing signal to be added.
D)A 3' splicing signal to be added.
E)It creates a polyadenylation signal.

Question 11

How do we differentiate between the positive and negative strands of a viroid genome?

A)The positive strand produces the viral protein.
B)The positive strand is transcribed to make the viral mRNA.
C)The positive strand is packaged into the viroid particle.
D)The positive strand is the only strand copied by a cellular RNA polymerase.
E)The positive strand is the most abundant RNA produced.

Question 12

When studying the replication of viroids and hepatitis delta virus,which of the following allows scientists to distinguish which of the three cellular RNA polymerases is required?

A)The sub-cellular location of each RNA polymerase.
B)Whether the polymerase requires an RNA primer or not.
C)Whether the polymerase can synthesize mRNAs or not.
D)Whether the polymerase will use an RNA molecule as a template.
E)The sensitivity of the RNA polymerase to the toxin $\alpha$ -amanitin.

Question 13

Viroid RNA molecules have a high degree of base pairing throughout the molecule.

Question 14

The typical structure of the genome of a viroid is described as?

A)Circular double-stranded DNA of 3000-4000bp.
B)Linear double-stranded RNA segment of 500-1000bps.
C)Circular singled-stranded RNA of 250-400nts.
D)Linear single-stranded RNA of 500-1000nts.
E)Circular double-stranded RNA of 400-800bp.

Question 15

Which of the following is a major difference between the group A and the group B viroids?

A)Whether they affect the RNAi pathway or not.
B)Whether they infect animals or plants.
C)Whether they produce a protein or not.
D)Whether they have a self-cleaving RNA or not.
E)Whether they replicate in the endoplasmic reticulum or not.

Question 16

Which of the following describes the major difference between hepatitis delta virus (HDV)and the plant viroids and satellite RNAs?

A)Only the HDV genome contains a ribozyme activity.
B)Only HDV requires a helper virus.
C)Only the HDV genome encodes a protein.
D)Only HDV replicates using a rolling circle mechanism.
E)Only HDV requires RNA polymerase II during its replication cycle.

Question 17

Which of the following is NOT thought to be a mechanism by which viroids cause disease in their plant hosts?

A)By basepairing to an important cellular RNA,preventing its function.
B)By activating the dsRNA induced protein kinase.
C)By causing the degradation of cellular mRNAs via the RNAi pathway.
D)By interfering with mRNA splicing because they resemble a cellular snRNA.
E)By inhibiting the machinery that exports mRNAs out of the nucleus.

Question 18

Which of the following is NOT a type of infectious RNA that can cause disease?

A)Viroid
B)Prion
C)Hepatitis delta virus
D)Satellite RNA
E)Viroid-like plant satellite RNA

Question 19

When the ribozyme activity in the avocado sunblotch viroid cleaves the RNA genome,which of the following describes the structure of the nucleotide on the 5' side of the cleavage?

A)It contains a 5' phosphate group
B)It contains a 3' phosphate group
C)It contains a 3'-OH group
D)It contains a 2',3'-cyclic phosphate
E)It contains a 3' hydrogen

Question 20

Viroids encode a single protein which is used to package the RNA for transmission between hosts.

Question 21

Coinfection with both hepatitis B and delta virus together makes the resulting liver disease less severe.

Question 22

There is some controversy about whether the replication of the hepatitis delta virus (HDV)genome is performed by the cellular RNA polymerase I or RNA polymerase II.Describe the evidence that supports each model.

Question 23

The enzymatic function that cleaves the avocado sunblotch viroid genome is called a ribozyme and does not require any proteins to function.

Question 24

Hepatitis delta virus is transmitted through the same pathways as hepatitis B virus.

Question 25

Describe how the ribozyme activity found in the plant virioids and hepatitis delta virus can be used as therapeutic agents to treat infections with other viruses.