1.
Which of the following is not true regarding viruses?
Correct Answer
C. All have a protein capsid and envelope
Explanation
All viruses have a protein capsid and envelope. This means that they have a protective protein coat (capsid) surrounding their genetic material, which can be either DNA or RNA. The envelope is an additional layer that some viruses have, which is derived from the host cell's membrane. It helps the virus to enter and exit host cells. Therefore, the statement "All have a protein capsid and envelope" is true.
2.
What type of immunity is most responsible for fighting viral infections?
Correct Answer
B. Cell-Mediated Immunity
Explanation
Cell-mediated immunity is the type of immunity that is most responsible for fighting viral infections. This form of immunity involves the activation of T cells, which directly attack and destroy virus-infected cells. T cells also release chemicals called cytokines that help coordinate the immune response and recruit other immune cells to the site of infection. In contrast, humoral immunity primarily involves the production of antibodies by B cells, which are more effective against bacterial infections. Innate immunity provides a general defense against various pathogens but is not specifically targeted towards viral infections.
3.
How are viruses different from bacteria?
Correct Answer
D. A and B
Explanation
Viruses are different from bacteria because they do not replicate by binary fission and they are smaller in size. Bacteria, on the other hand, replicate through binary fission and are larger in size compared to viruses. Therefore, the correct answer is A and B.
4.
Which is not true regarding adsorption?
Correct Answer
C. Requires ATP
Explanation
Adsorption is the process by which a virus attaches to a host membrane. It is a random and reversible process, meaning that the virus can attach and detach from the host membrane. Nonenveloped viruses attach to host cells via exposed capsid regions. However, adsorption does not require ATP (adenosine triphosphate), which is the energy currency of cells. Therefore, the statement "Requires ATP" is not true regarding adsorption.
5.
Viruses are classified according to all of the following except:
Correct Answer
E. Structure of virus
Explanation
Viruses are classified based on several criteria, including their type of replication (DNA or RNA, replication strategy), the structure of their infectious particle (virion), the host organism they infect, and the type of nucleic acid in their genetic material. However, they are not classified solely based on the "Structure of virus" criterion, as this aspect is considered as part of the "Structure of virion" in virus classification.
6.
Which is not true regarding capsids?
Correct Answer
D. Only A and B
Explanation
The correct answer is "Only A and B". This means that the statements "composed of repeating subunits" and "able to self-assemble into virions" are true regarding capsids. Capsids are protein coats that enclose and protect the genetic material of viruses. They are composed of repeating subunits, which allow for self-assembly into complete virions. The statement about the helical structure having a fixed number of subunits and being spherical in shape is not true, as helical capsids can have varying numbers of subunits and do not necessarily have a spherical shape.
7.
A particular virus' genetic material first needs to be copied into positive sense SS-RNA (Single Strand RNA). What type of virus is this?
Correct Answer
B. SS Negative-Sense RNA
Explanation
Negative-sense RNA viruses have a genetic material consisting of negative-sense RNA, which means that their RNA strand is complementary to the messenger RNA (mRNA) needed for protein synthesis. To replicate and express their genes, they must first transcribe their negative-sense RNA into positive-sense RNA, which can then serve as a template for protein production.
8.
Primary replication of the virus takes place before spread. This happens with:
Correct Answer
B. Hematogenous spread
Explanation
Hematogenous spread refers to the spread of a virus through the bloodstream. In the context of the given question, it suggests that the primary replication of the virus occurs before it spreads through the bloodstream. This means that the virus initially infects a specific organ or tissue, replicates within it, and then enters the bloodstream to spread to other parts of the body. This explanation implies that neural spread, tissue spread, and viremia are not the primary modes of virus replication and spread in this case.
9.
Adenoviidae, Poxviridae, and Herpesviridae are:
Correct Answer
C. Double-stranded DNA
Explanation
Adenoviidae, Poxviridae, and Herpesviridae are classified as double-stranded DNA viruses. This means that their genetic material consists of two strands of DNA, which are complementary to each other. These viruses replicate their DNA using a double-stranded intermediate, and their genome is stable and can be integrated into the host cell's DNA. This classification is based on the structure and characteristics of the viruses, as well as their mode of replication.
10.
Which of the following is mixed-stranded?
Correct Answer
D. Hepadnoviridae
Explanation
Hepadnoviridae is the correct answer because it is the only option among the given choices that is known to have mixed-stranded DNA. Mixed-stranded DNA refers to a DNA molecule that contains both a single-stranded and double-stranded regions. The other options listed are all single-stranded RNA viruses, which do not have mixed-stranded DNA.