All Free Biology MCQs with Answers

2331. Which of the following virus has special affiliations with the tumor production:

• A. Hepatitis virus
• B. Retrovirus
• C. Polio virus
• D. Pox virus

Explanation: Retroviruses have a strong association with tumour formation because some carry oncogenes or can activate host genes after integrating their DNA into the host genome. Hepatitis viruses can also contribute to certain cancers, but retroviruses are the specifically recognized tumour-associated group in this set.

2332. The agent of controversial nature causing mad cow infection is_____________?

• A. Bacteria
• B. Cowpox Virus
• C. Adenovirus
• D. Prion

Explanation: Mad cow disease, or bovine spongiform encephalopathy, is caused by a prion, an infectious misfolded protein lacking a conventional nucleic-acid genome. Students may choose a virus because the disease is transmissible, but transmissibility alone does not make its agent viral.

2333. Which of the following is the smallest known virus:

• A. Hepatitis virus
• B. Retrovirus
• C. Polio virus
• D. Pox virus

Explanation: Among these options, poliovirus is the smallest, with a compact, non-enveloped capsid and a genome of roughly 7.5 kilobases. Poxviruses are among the largest viruses, and retroviruses and hepatitis viruses are larger than poliovirus, so students may incorrectly associate small size with any simple virus.

2334. An isolated virus is not considered living since it________________?

• A. Separates in to two inner parts
• B. Can not metabolize
• C. Rapidly looses its Genome chemical inert
• D. Is coated with an air tight shield

Explanation: An isolated virus cannot perform independent metabolism because it lacks cellular machinery such as ribosomes and metabolic enzymes. Students may choose the genome-related option because viral particles can lose infectivity outside a host, but the fundamental reason they are not considered independently living is their metabolic dependence.

2335. Bacteriopahage that infect E. coli are called_____________?

• A. M type
• B. N type
• C. T type
• D. S type

Explanation: The bacteriophages that infect Escherichia coli are classically called T phages, including T1 through T7. The other lettered types are not the standard designation for this well-known group, so students may guess another letter without recalling the T-phage examples.

2336. Attachment of the bacteriophage with the receptor site on the bacterial cell wall involves_______________?

• A. Strong covalent bond between virion and the receptor site.
• B. Week chemical unior between them
• C. Both A and B depending upon the phage
• D. None of these

Explanation: Phage attachment to a bacterial receptor is a specific, reversible interaction involving weak non-covalent forces rather than a strong covalent bond. Students may choose both A and B because they interpret attachment as requiring a permanent chemical linkage, but covalent bonding would prevent the normal reversible recognition step.

2337. Mode of transmission of hepatitis A is__________?

• A. Serum
• B. Faeco-oral
• C. Sexual contact
• D. All of these

Explanation: Hepatitis A virus is mainly transmitted by the faeco-oral route, when contaminated food or water carries the virus from faeces into another person's mouth. Sexual transmission can occur in some circumstances, but serum transmission is not the standard route, so “all of these” is too broad for the usual mode of transmission.

2338. Protein coat the capsid of adenovirus is________________?

• A. Surrounded by genome
• B. Surrounding genome
• C. Surrounding the envelope
• D. Both B and C

Explanation: The capsid is the protein shell that encloses and protects the viral genome. Adenovirus is non-enveloped, so its capsid surrounds the genome and there is no envelope for it to surround. Students may choose d by confusing the capsid with the envelope found in enveloped viruses.

2339. For which of the following no preventive vaccine is available?

• A. HAV
• B. HBV
• C. HCV
• D. HEV

Explanation: No routinely available preventive vaccine exists for hepatitis C because HCV has extensive genetic variation and changes its surface antigens, allowing it to evade immune responses. Vaccines are available for HAV and HBV, and an HEV vaccine is available in some countries. Students may choose d because hepatitis E is also commonly discussed as a vaccine-preventable hepatitis.

2340. A virion is______________?

• A. Virus
• B. Viral protein
• C. Viral lysozyme
• D. Viral gene

Explanation: A virion is a complete, mature virus particle outside a host cell, consisting of viral nucleic acid enclosed by a capsid and sometimes an envelope. It is not merely a protein, enzyme or isolated gene. Students may choose d by confusing the viral genome with the complete infective particle.