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 #2 : Molecular Biology And Genetics
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
I, II, and III
I only
III only
I and III
I only
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 #3 : Molecular Biology And Genetics
Which type of virus uses reverse transcriptase in order to convert its genome into a viable template for reproduction?
Retroviruses
Double-stranded RNA viruses
Single-stranded RNA viruses
Single-stranded DNA viruses
Retroviruses
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 #2 : Viruses
Which of the following is the correct sequence for viral replication?
Replication, viral assembly, transcription, protein synthesis, penetration, release
Release, replication, transcription, protein synthesis, viral assembly, penetration
Penetration, replication, transcription, protein synthesis, viral assembly, release
Transcription, protein synthesis, replication, viral assembly, release, penetration
Viral assembly, release, penetration, transcription, protein synthesis, replication
Penetration, replication, transcription, protein synthesis, viral assembly, release
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 #1 : Viruses
Why do viral proteins interact with each other extensively as well as interact with a wide array of host proteins?
Viruses encode a small number of proteins compared to the host
Viral proteins exhibit numerous, small, low-specificity binding sites
To modulate host cellular activities
Viral proteins have many splice variants
All of these
All of these
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 #1 : Viruses
What enzyme would a non retroviral RNA virus use to replicate it's genome?
An RNA dependent DNA polymerase encoded by the virus
An RNA dependent RNA polymerase encoded by the virus
An RNA dependent RNA polymerase encoded by the host
A DNA dependent RNA polymerase encoded by the virus
A DNA dependent RNA polymerase encoded by the virus
An RNA dependent RNA polymerase encoded by the virus
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.
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