Deck 30: Hepadnaviruses

Question 1

Which of the following is a likely purpose for the noninfectious particles produced by hepatitis B virus?

A)They bind to antibodies allowing the virus to evade the immune system.
B)They bind to the host cell receptor,improving entry of virus particles.
C)They stimulate cytotoxic T lymphocytes.
D)They bind to liver cells and stimulate them to replicate.
E)They are just packaging mistakes that occur in some cells and they serve no purpose.

Answer 1

A

Question 2

The copy of the hepatitis B virus genome that is inside of the virion has unusual structures as the 5' and 3' ends.Which of the following describes the genome ends?

A)The 5' end has a cap structure and the 3' end has a poly(A)tail.
B)The 5' end has a triphosphate and the 3' end has a hydroxyl group.
C)The 5' end has a fragment of RNA and the 3' end has a protein attached.
D)The 5' end has a protein attached and the 3' end has a fragment of RNA.
E)There are no ends,the genome is a covalently closed circle.

Answer 2

D

Question 3

Which of the following mechanisms is used by hepatitis B to get the viral genome packaged into the virion?

A)The polymerase interacts with both the pregenomic mRNA and the capsid protein.
B)The capsid protein interacts with the completed DNA genome.
C)The capsid is assembled around the completed DNA genome.
D)The large surface antigen interacts with the completed DNA genome.
E)The large surface antigen interacts with both the pregenomic mRNA and the capsid protein.

Answer 3

A

Question 4

Which of the following explains why there is a gap in the DNA genome of hepatitis B virus?

A)There is a segment of RNA that can't be removed from this region of the genome.
B)There are proteins bound to the template that block the polymerase.
C)The polymerase enzyme runs out of deoxynucleotide triphosphates.
D)The complementary strand can't base pair in this region of the genome.
E)This is where the genome integrates into the host chromosome.

Question 5

The longest open reading frame in the genome of hepatitis B virus genome encodes which of the proteins?

A)The E protein.
B)The X protein.
C)The largest surface antigen.
D)The capsid protein.
E)The reverse transcriptase enzyme.

Question 6

The early steps of hepatitis B virus replication in an infected cell are poorly understood.Which of the following explains why?

A)It is difficult to get hepatitis B virions to enter the host cell.
B)Hepatitis B virus kills the infected cells too quickly.
C)There are no cultured cells that can be productively infected with the virus.
D)There are no antibodies available that can bind to the envelope proteins.
E)There is not a good animal model that mimics the hepatitis B virus infection.

Question 7

It is recommended that people in certain professions or with certain disease should receive the hepatitis B vaccine.For which of the following individuals would it NOT be critical for them to be vaccinated against hepatitis B?

A)Zoo keeper
B)Nurse
C)Tattoo-parlor worker
D)Barber
E)Hemophiliac

Question 8

The membrane binding domain for all three surface antigens from hepatitis B virus is located at which of the following locations?

A)It is in the common N terminal domain,which is the large surface protein region.
B)It is in the common C terminal domain,which is the small surface protein domain.
C)The surface antigens have a myristate attached to the large protein domain.
D)The transmembrane alpha helices are found in the middle antigen region of the protein.
E)It is located in a beta-barrel structure found in the large surface antigen.

Question 9

A new method of preventing transmission of hepatitis B virus,called immunoprophylaxis,is described by which of the following statements?

A)Stimulation of the production of anti-hepatitis B antibody production using a vaccine.
B)Use of anti-hepatitis antibodies to bind to virus present in blood donations.
C)Injection of cytotoxic T cells into a chronically infected patient.
D)Injection of anti-hepatitis B antibodies into newborns.
E)Stimulation of immune response against hepatitis B using interferon.

Question 10

The drug Lamivudine (3TC)has been shown to inhibit which step in the infectious cycle of hepatitis B virus?

A)Binding and entry into the host cell.
B)Reverse transcription of the viral genome.
C)Transcription of the viral genome.
D)Translation of the viral mRNAs.
E)Assembly of new virions.

Question 11

All of the following describe similarities between the reverse transcription process in retroviruses and hepadnaviruses EXCEPT:

A)They both use a virally encoded reverse transcriptase enzyme.
B)They both use a protein primer to begin DNA synthesis.
C)They both produce a double-stranded DNA product.
D)They both require the presence of repeat sequences in the viral RNA.
E)They both use a ribonuclease H enzyme activity during reverse transcription.

Question 12

Which of the following mechanisms prevents packaging of the preC mRNA into the virion of hepatitis B virus?

A)Binding of the P protein to the packaging site prevents the C protein from binding.
B)Binding of the C protein to the packaging site prevents the P protein from binding.
C)Translation of the C open reading frame blocks the packaging site.
D)Translation of the preC reading frame blocks the packaging site.
E)Translation of the P open reading frame blocks the packaging site.

Question 13

Which of the following occurs immediately after entry of the hepatitis B virus genome into the host cell?

A)Translation of the viral genome into proteins.
B)Integration of the viral genome into the host genome.
C)Reverse transcription of the genome into double-stranded DNA.
D)Transcription of the viral genome to make mRNAs.
E)Conversion of the genome to a covalently closed circular form.

Question 14

Like retroviruses,hepatitis B virus (HBV)uses a reverse transcription step.Which of the following distinguishes HBV from the retroviruses?

A)HBV has an enveloped virion.
B)HBV packages a DNA genome in the virion.
C)HBV packages reverse transcriptase enzyme in the virion.
D)HBV fuses its envelope with the cellular plasma membrane.
E)All of the above distinguish HBV from retroviruses.

Question 15

Hepatitis B virus produces both infectious and noninfectious particles.Only the infectious particles contain the large surface antigen.Which of the following explains why?

A)The small and medium surface antigens are sequestered in the ER.
B)The small and medium surface antigens are sequestered in the noninfectious particles.
C)Only the large surface antigen is retained in the endoplasmic reticulum.
D)Only the large surface antigen is found on the plasma membrane.
E)Only the large surface antigen interacts with the core protein.

Question 16

Which of the following describes the control sequences that hepatitis B viruses uses to direct transcription and processing of the viral mRNAs?

A)There are 5 promoters and 1 polyadenylation site.
B)There are 3 promoters and 2 polyadenylation sites.
C)There are 2 promoters and 2 polyadenylation sites.
D)There is only 1 promoter and 1 polyadenylation site.Different mRNAs are produced via alternative mRNA splicing.
E)The virus only produces a single mRNA which is the pregenomic mRNA.

Question 17

The hepatitis B genome as it is found inside the virion has an unusual structure.Which of the following is NOT a characteristic of the virion genome?

A)It has a gap of single-stranded DNA.
B)It has an inverted repeat at each end of the genome.
C)It has a piece of RNA attached to the 3' end of the genome.
D)The plus strand is shorter than the minus strand.
E)It has a protein covalently attached to the 5' end of the genome.

Question 18

Which of the following describes an interesting feature of the preC and pregenomic mRNAs produced by the hepatitis B virus?

A)They are extensively spliced to produce a set of nested mRNAs.
B)They are transcribed by the cellular RNA polymerase III enzyme.
C)They are produced by the reverse transcriptase enzyme.
D)They are transcribed past a polyadenylation site near the promoter.
E)They each code for several proteins due to the use of alternative start codons.

Question 19

Hepatitis B is usually transmitted via the oral-fecal route.

Question 20

Scientists have generated mice that synthesize the X protein from hepatitis B virus in all of the liver cells.Which of the following describes the effect of the X protein on mice?

A)When infected with hepatitis B,they have a greater amount of liver damage.
B)When infected with hepatitis B,they develop a less severe liver disease.
C)They are predisposed to developing liver cancer.
D)They are resistant to infection with hepatitis B.
E)The X protein by itself can induce a hepatitis-like disease.

Question 21

The unusual structure of the of the hepatitis B virus genome found in the virion is a result of the mechanism used to replicate the genome.

Question 22

Describe the methods used to both prevent and treat hepatitis B virus (HBV)infections.

Question 23

The polymerase protein from hepatitis B virus binds to the epsiolog ( $\varepsilon$ )stem-loop on the pregenomic mRNA,which is important for packaging of the genome into the capsid.

Question 24

Like retroviruses,the genome of hepatitis B virus is integrated into the genome of the host cell.

Question 25

Compare and contrast the genome replication cycles of retroviruses and hepadnaviruses,like hepatitis B virus.

Question 26

The X protein from hepatitis B virus is thought to activate gene transcription because it is found in the nucleus of infected cells.

Question 27

Hepatitis B replication is completely limited to hepatocytes.

Question 28

Scientists are currently testing an edible vaccine for hepatitis B virus by engineering the antigens into bananas.