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Example Questions
Example Question #1 : Viral Genetics
When mutating a virus for vaccine development, which of the following characteristics would not be an ideal outcome?
no antigenicity
altered host range
altered target cell specificity
reduced pathogenicity
no antigenicity
A mutated virus for vaccine development must retain antigenicity in order to induce an immune response in the recipient. Reduced pathogenicity, altered host range, or altered target cell specificity would all be desired traits in a vaccine strain.
Example Question #1 : Viral Genetics
Why do RNA viruses have mutation rates higher than those of DNA viruses?
RNA viruses lack a proofreading function in the replicatory enzymes.
RNA viruses have a more redundant genetic code
RNA viruses are smaller
RNA viruses are larger
RNA viruses lack a proofreading function in the replicatory enzymes.
Viral RNA polymerases do not have the same proof-reading ability as DNA polymerases. This is a contributing factor to the difficulty of making vaccines from RNA viruses.
Example Question #2 : Viral Genetics
Retroviruses are not considered RNA viruses because __________.
they use DNA intermediates to replicate
they are single-stranded
they are double-stranded
they have a DNA genome
they use DNA intermediates to replicate
Retroviruses do have a single-stranded RNA genome, but they use DNA intermediates in replication. Retroviruses utilize reverse transcriptase to convert viral RNA into complementary DNA, which is then copied to produce double-stranded viral DNA.
Example Question #3 : Viral Genetics
Choose the correct answer:
The process by which viruses that have segmented genomes trade segments during replication is known as __________.
mutation
biosynthesis
independent assortment
incomplete linkage
independent assortment
Recombination by independent assortment occurs in viruses that have segmented genomes. Genes are randomly assorted, which can result in the generation of viruses with new antigenic determinants (antigenic shift).
Example Question #4 : Viral Genetics
Retroviruses use __________ to make DNA from their own RNA, before inserting the DNA into the host cell’s genome.
retrotransposons
endocytosis
telomerase
reverse transcriptase
membrane fusion
reverse transcriptase
Reverse transcriptase is an enzyme that can transcribe DNA from RNA, and is used by retroviruses to make a DNA transcript of their own RNA genome. The DNA is then inserted directly into the host’s genome. Endocytosis and membrane fusion are different terms for the process by which viruses insert material into the host cell, but not directly into the genome. Retrotransposons are genetic elements in eukaryotic cells that use reverse transcriptase to duplicate themselves throughout the cell genome. Telomerase is a type of reverse transcriptase found in eukaryotic cells that adds repeated sequences to the ends of chromatids.
Example Question #5 : Viral Genetics
A virus that has not yet entered a host cell contains what type of genetic material?
RNA
Viruses only produce genetic material after entering a host cell.
DNA
RNA and DNA
RNA or DNA
RNA or DNA
Viruses are not universally recognized as living organisms. One of many differences between viruses and other organisms is that all other living organisms contain both DNA and RNA, while viruses only contain one or the other. Some RNA viruses are able to produce DNA using mechanisms such as reverse transcription, but this does not happen until after the virus infects the host cell.
Example Question #6 : Viral Genetics
The process through which segments of different, but similar strains, of viruses in the same cell are combined together to form a new virus is termed what?
Genetic drift
Transduction
Antigenic drift
Conjugation
Antigenic shift
Antigenic shift
In a cell infected by more than one strain of virus, the segments of the different strains can be combined during viral assembly. Transduction is when DNA is introduced to a cell by a viral vector. Conjugation is when bacteria insert genes into other cells, usually other bacteria, using a pillus. Genetic drift is a term in evolution that applies to all organisms, where allele frequencies in a population change due to random chance. Antigenic drift is when viruses accumulate mutations over time.
Example Question #7 : Viral Genetics
Viruses are classified in part by the type of genetic material they contain. Which of the following is not a classification of viruses?
Double-stranded DNA viruses
All are classifications of viruses
Single-stranded RNA viruses
Single-stranded DNA viruses
Double-stranded RNA viruses
All are classifications of viruses
Viruses have an enormous variety of genome structures, more than any phylum of organism. They have a variety of ways of expressing their genes and replicating, all involving using the host cell’s own machinery.
Example Question #8 : Viral Genetics
Fill in the blanks:
Viruses with __________-fidelity transcriptases have __________ mutation rates.
high . . . undetectable
high . . . high
low . . . low
high . . . low
high . . . low
Viruses that have high-fidelity transcriptases have relatively low mutation rates. Conversely, viruses with low-fidelity transcriptases have relatively high mutation rates. Generally, the higher the fidelity of any enzyme involved in replication of viral nucleic acid, the lower the mutation rate.
Example Question #10 : Viral Genetics
What part(s) of the virus structure assists in invading host cells?
spikes
capsid
enzyme
DNA
RNA
spikes
Spikes are either composed of hemagglutinin protein (HA) or protein neuraminidase (NA). HA helps the virus link with the host cell membrane while NA allows the release of a newly formed viral particle from the host cell.
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