GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Viral Replication

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

Example Question #1 : Help With Viral Replication

An inhibitor that prevents reverse transcription would be most useful in combatting which of the following viruses?

I. Retroviruses

II. DNA viruses

III. RNA viruses

Possible Answers:

I, II, and III

III only

I only

I and III

Correct answer:

I only

Explanation:

Of the three choices, only retroviruses use reverse transcription to make a DNA copy of their RNA genomes.

DNA viruses do not need to do this because their genome already consists of DNA. RNA viruses use specialized enzymes called RNA replicases to make RNA copies of their RNA genomes, and do not go through a DNA intermediate like retroviruses. 

Example Question #2 : Help With Viral Replication

Which type of virus uses reverse transcriptase in order to convert its genome into a viable template for reproduction?

Possible Answers:

Single-stranded DNA viruses

Double-stranded RNA viruses

Single-stranded RNA viruses

Retroviruses

Correct answer:

Retroviruses

Explanation:

Reverse transcriptase is used to convert RNA genomes into DNA genomes. The genome is then inserted into the host's chromosomes, where it can be transcribed numerous times to create viral proteins. Without this process, the RNA genome would have a very short-lived existence in the cell, resulting in very few viral copies.

This technique is used by retroviruses, such as HIV.

Example Question #3 : Help With Viral Replication

Which of the following is the correct sequence for viral replication?

Possible Answers:

Release, replication, transcription, protein synthesis, viral assembly, penetration

Penetration, replication, transcription, protein synthesis, viral assembly, release

Viral assembly, release, penetration, transcription, protein synthesis, replication

Replication, viral assembly, transcription, protein synthesis, penetration, release

Transcription, protein synthesis, replication, viral assembly, release, penetration

Correct answer:

Penetration, replication, transcription, protein synthesis, viral assembly, release

Explanation:

The first step in viral replication is penetration. The virus may be engulfed by the host cell or fuse with the host's membrane. The viral genetic material is released into the cytoplasm. During replication the viral genetic material is copied many times. The viral genetic material is used as a blueprint to make messenger RNA (mRNA) during the transcription stage. The mRNA is used to synthesize viral proteins. The viral genetic material and enzymes are surrounded by their protein coat during viral assembly. Finally viruses are released from the host cell by budding from the cell membrane or bursting the cell. 

Example Question #4 : Help With Viral Replication

Why do viral proteins interact with each other extensively as well as interact with a wide array of host proteins? 

Possible Answers:

All of these

To modulate host cellular activities

Viruses encode a small number of proteins compared to the host

Viral proteins have many splice variants

Viral proteins exhibit numerous, small, low-specificity binding sites

Correct answer:

All of these

Explanation:

All of the answers are correct. Given that viral genomes are small, the proteins that they encode must be able to execute many functions. Due to high mutation rate, many splice variants, and multiple small protein binding domains, viral proteins interact extensively with each other and host proteins. This allows viral proteins to modulate host cellular activities such as inflammation, proliferation, anti-viral response, and DNA replication/transcription/translation so that viral proteins are able to replicate and are not killed by the infected cells. 

Example Question #5 : Help With Viral Replication

What enzyme would a non retroviral RNA virus use to replicate it's genome? 

Possible Answers:

An RNA dependent DNA polymerase encoded by the virus

An RNA dependent RNA polymerase encoded by the host

An RNA dependent RNA polymerase encoded by the virus

A DNA dependent RNA polymerase encoded by the virus

A DNA dependent RNA polymerase encoded by the virus

Correct answer:

An RNA dependent RNA polymerase encoded by the virus

Explanation:

In order the replicate its genome, a non retroviral RNA virus must use a polymerase that can use an RNA template to polymerize a complimentary RNA molecule; an RNA dependent RNA polymerase. Since no such enzyme exits in host cells, the virus must encode this enzyme itself.

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
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