All Free Biology MCQs with Answers

2321. In the lytic cycle of bacteriophage the host DNA is__________?

• A. Replicated
• B. Turn off by the protein coat.
• C. Digested into its nucleotides
• D. Turned on by the removal of the protein coat

Explanation: During the lytic cycle, bacteriophage nucleases break the host bacterial DNA into nucleotides, which can then be reused for making viral components. Students may choose replication because the viral genome is replicated, but it is the phage DNA, not the host DNA, that is replicated at this stage.

2322. Which of the following is an RNA virus:

• A. Influenza virus
• B. Herpes virus
• C. HBV
• D. Pox virus

Explanation: Influenza virus contains RNA as its genetic material, specifically segmented single-stranded RNA. Herpesvirus, hepatitis B virus, and poxvirus are DNA viruses, so students often select HBV because they remember hepatitis as a viral disease without distinguishing its genome type.

2323. Temperate phage may exist as_____________?

• A. Prophage
• B. Capsid
• C. Viron
• D. Retrovirus

Explanation: A temperate phage can integrate its DNA into the bacterial chromosome, where it is called a prophage. A capsid is the protein coat, and a virion is a complete virus particle, so these terms describe structures rather than the integrated state of a temperate phage.

2324. In the Lysogenic cycle the DNA of the bacteriophage__________________?

• A. Joins the bacterial chromosomes
• B. Attaches to the inner surface of the host membrane
• C. Is immediately degraded when enters the host
• D. Goes directly to host ribosomes for translation

Explanation: In the lysogenic cycle, bacteriophage DNA becomes integrated into the bacterial chromosome and is replicated with the host DNA as a prophage. Students may choose the ribosome option because viral genes are eventually expressed, but integration occurs before translation.

2325. Tobacco mosaic virus is__________?

• A. Spherical
• B. Rod Shaped
• C. Tadpole like
• D. Hexagonal

Explanation: Tobacco mosaic virus has a rigid helical capsid that gives the virion a characteristic rod-shaped form. The spherical and hexagonal choices refer to other possible viral shapes, while the tadpole-like form is typical of many bacteriophages.

2326. In life cycle of bacteriophage which step occur after attachment of prophage with the receptor site of the bacterial cell wall_____________?

• A. Absorption
• B. Multiplication
• C. Lysogeny
• D. Penetration

Explanation: After a phage attaches, or adsorbs, to receptors on the bacterial cell wall, it injects its nucleic acid into the host during penetration. Multiplication and lysogeny occur later, so students who choose multiplication are skipping the entry step.

2327. Which of the following disease results in Paralysis due to viral attack on C.N.S:

• A. Measles
• B. Herpes simplex
• C. Hepatitis
• D. Polio

Explanation: Poliovirus attacks motor neurons in the central nervous system and can cause paralysis. Measles and hepatitis primarily produce other systemic effects, while herpes simplex can affect the nervous system but is not the classic viral cause of paralytic disease in this list.

2328. In lysogenic cycle the process of spearation of phage DNA from the hosts chromosome and initiation of lytic cycle is called______________?

• A. Lysis
• B. Lysogeny
• C. Induction
• D. Adsorption

Explanation: Induction is the excision of prophage DNA from the bacterial chromosome followed by entry into the lytic cycle, often after environmental stress. Lysis is the later rupture of the host cell, so students may choose it by focusing on the final outcome rather than the initiating process.

2329. An enzyme which can convert single stranded RNA into double stranded viral DNA is called____________?

• A. DNAase
• B. RNAase
• C. DNA polymerase
• D. Reverse Transcriptase

Explanation: Reverse transcriptase uses an RNA template to synthesize complementary DNA and can ultimately produce double-stranded viral DNA. DNAase and RNAase are nucleases that degrade nucleic acids, while ordinary DNA polymerase does not normally copy RNA into DNA.

2330. Which of the following is incorrect for the lysogenic cycle in life cycle of bacteriophage_____________?

• A. Phage when gets incorporated with the bacterial chromosome is called prophage
• B. The bacterium continues to live and reproduce normally
• C. Lysogenic bacteria may get infected by the related phage
• D. The cycle may convert into lytic type resulting from environmental exposure

Explanation: A lysogenic bacterium containing a prophage is generally immune to superinfection by the same or a closely related phage because prophage genes block reinfection. Therefore the statement that it may be infected by a related phage is incorrect; students may accept it by overlooking lysogenic immunity.