All Free Biology MCQs with Answers

2881. Proteins that cause disease in humans and animals are called:

• A. Prions
• B. Viroid
• C. Prophage
• D. Bacteriophage
• E. Antigens

Explanation: Prions are misfolded proteins that can induce other proteins to also misfold, leading to the accumulation of abnormal protein structures in cells. This can result in neurodegenerative diseases, such as Creutzfeldt-Jakob disease in humans and mad cow disease in cattle. Prions are unique because they can propagate without nucleic acids (DNA or RNA), making them distinct from other infectious agents like bacteria and viruses.

2882. Which virus kills cancer cells and aids immunity?

• A. Saccharomyces
• B. Lactobacillus
• C. Penicillium
• D. Lymph Bacterium
• E. Oncolytic

Explanation: Oncolytic viruses are viruses designed or naturally able to infect and destroy cancer cells while sparing normal tissue. They enter tumor cells, replicate inside them, and eventually cause those cells to break apart, which helps shrink the tumor and also alerts the immune system to attack remaining cancer cells.

2883. Which of the following is an example of a sub-viral particle that infects plants?

• A. Prion
• B. Viroid
• C. Bacteriophage
• D. Infectious protein

Explanation: Viroids are small, circular RNA molecules that can infect plants. They lack a protein coat and do not encode proteins, relying on the host's cellular machinery for replication. Viroids are responsible for various plant diseases, disrupting normal growth and development

2884. Bacteriophages escape from host cells by the activity of:

• A. Non-Ribosome
• B. Lysozyme
• C. Peroxisome
• D. Lysosome

Explanation: Lysozyme is an enzyme that plays a crucial role in the immune system and is involved in breaking down bacterial cell walls.

2885. Phage genome incorporated with host DNA is called:

• A. Bacteriophage
• B. Viroids
• C. Prophage
• D. Prions

Explanation: A prophage is the latent form of a bacteriophage (a virus that infects bacteria) when it integrates its genetic material into the bacterial chromosome. In this state, the viral DNA is replicated along with the bacterial DNA during cell division without causing immediate harm to the host. The prophage can remain dormant for extended periods, but under certain conditions, it may reactivate and enter the lytic cycle, leading to the production of new viral particles and the lysis of the bacterial cell. Prophages can play a role in horizontal gene transfer, contributing to genetic diversity among bacteria and sometimes providing advantageous traits, such as antibiotic resistance. Understanding prophages is important in microbiology and virology, particularly in studying bacterial evolution and the dynamics of bacterial infections.

2886. Example of viruses having a polyhedral capsid that is with 252 capsomeres is:

• A. Adenovirus
• B. Tobacco Mosaic Virus
• C. Influenza virus
• D. Bacteriophage

Explanation: The capsid of adenovirus typically contains 52 capsomeres. This includes 240 hexon capsomeres and 12 penton capsomeres at the vertices.

2887. The complete, mature & infectious particle of virus is known as:

• A. Genome
• B. Capsomere
• C. Virion
• D. Envelope

Explanation: A virion is the fully assembled, infectious form of a virus when it's outside a host cell. It includes the genetic material along with its protective protein coat, and sometimes an envelope, allowing it to survive in the environment and infect new cells.

2888. The causative organism of measles is:

• A. Poxivirus
• B. Paporivirus
• C. Picornovirus
• D. Paramyxovirus

Explanation: Measles is caused by the measles virus, which is an RNA virus belonging to the Morbillivirus genus within the Paramyxoviridae family. The virus primarily infects the respiratory tract and can spread throughout the body, leading to the characteristic symptoms of measles, including fever, cough, runny nose, conjunctivitis, and the distinctive rash.

2889. In the life cycle of a bacteriophage, the lysozymes are required in which of the following steps of the infection process?

• A. Genome injection
• B. Penetration
• C. Replication
• D. Adsorption

Explanation: Penetration in the context of bacteriophages refers to the process by which the phage injects its genetic material into a bacterial host cell after successfully adsorbing to the bacterial surface. This step is critical for the viral life cycle as it enables the phage to hijack the host's cellular machinery to replicate and produce new phage particles. L ysozyme hydrolyzes the peptidoglycan layer in bacterial cell walls, leading to cell lysis and death

2890. During which stage of bacteriophage replication, lysozyme is involved?

• A. Adsorption
• B. Attachment
• C. Multiplication
• D. Penetration

Explanation: The bacteriophage releases lysozyme, an enzyme that breaks down the bacterial cell wall, allowing the viral genetic material to enter and later helping in the release of new phages by breaking open the cell.