Free Biodiversity and Variety of Life MCQs with Answers

641. When a virus enters a cell and incorporates its RNA or DNA into host DNA, what is this stage called?

• A. Lysogeny
• B. Fermentation
• C. Symbiosis
• D. Synergism

Explanation: The correct answer is A, as the stage when a virus enters a cell and incorporates its RNA or DNA into host DNA is called lysogeny. Fermentation is a metabolic process that produces energy without oxygen. Symbiosis is a relationship between two organisms that benefits both organisms. Synergism is a situation in which two or more substances work together to produce an effect that is greater than the sum of their individual effects. None of these terms accurately describes the stage when a virus enters a cell and incorporates its RNA or DNA into host DNA.

642. A phage when viral DNA is incorporated into host DNA is referred to as:

• A. T4 phage
• B. Provirus
• C. Prophage
• D. Bacteriophage

Explanation: The correct answer is C) prophage. A prophage is a phage genome that has been incorporated into the host cell's DNA. It is essentially a dormant phage that can be reactivated to cause an infection." "T4 phage," "provirus," and "bacteriophage" are all terms that refer to different types of viruses.

643. Infectious RNA without capsid:

• A. Virion
• B. Viroid
• C. Prion
• D. Virus

Explanation: The answer is B) viroid. A viroid is a small, infectious RNA molecule that does not have a protein coat (capsid). Viroids are the smallest known infectious agents. They are able to replicate in plants, but they cannot infect animals or humans. A virus is a small, infectious agent that can replicate only inside the living cells of an organism. Viruses can be classified into 3 groups. A prion is a misfolded protein that can transmit its misfoldedness to normal variants of the same protein and trigger cellular death. A virion is a complete virus particle, including the nucleic acid (DNA or RNA) and the protein coat.

644. What does the size of a virus range between?

• A. 100 mm to 150 mm
• B. 20 nm to 250 nm
• C. 300 nm to 3000 nm
• D. 3 nm to 30 nm

Explanation: The size of a virus ranges between 20 nm and 250 nm.

645. What is a provirus?

• A. Free virus
• B. Free DNA
• C. Primitive virus
• D. Integrated viral genome

Explanation: The correct option is D, as a provirus is the form of a retrovirus that is integrated into the host cell's DNA. It is essentially a dormant virus that can be reactivated to cause an infection.

646. What is the function of a viral capsid?

• A. Protection against the viral genome from physical and enzymatic destruction.
• B. Providing binding sites that enable the virus to attach to specific receptor sites on the host cell.
• C. Serving as a vehicle of transmission from one host to another.
• D. All of the above

Explanation: The viral capsid is a protein shell that protects the viral genome from damage and enzymatic degradation, allows the virus to attach to specific host cell receptors, and helps transmit the virus between hosts. It is essential for safeguarding the genome, enabling infection, and supporting viral spread.

647. Which of the following viruses is enveloped?

• A. Adenovirus
• B. Herpes virus
• C. Poliovirus
• D. None of these

Explanation: The correct option is B, as out of all the above-mentioned viruses, only the herpes virus is an enveloped virus, as it has a lipid envelope surrounding its capsid.Poliovirus and adenovirus are naked viruses and do not have an envelope around their capsid.

648. Which of the following is not a described type of virus?

• A. Virus containing single strand DNA
• B. Virus containing double strand DNA
• C. Virus containing single strand RNA
• D. Virus containing single strand RNA and single strand DNA

Explanation: Option D is correct, as viruses can be classified into two groups based on their genetic material: DNA viruses and RNA viruses. DNA viruses have a double-stranded DNA genome, while RNA viruses have either a single-stranded RNA genome or a double-stranded RNA genome. There is no known virus that has both a single-stranded RNA genome and a single-stranded DNA genome.

649. The size of viruses is usually measured in:

• A. Centimeters
• B. Micrometers
• C. Nanometers
• D. Millimeters

Explanation: Viruses are microscopic organisms measured in nanometers. They can range from 20 nm to 400 nm.

650. Icosahedral viruses have how many faces?

• A. 20
• B. 30
• C. 10
• D. 40

Explanation: Fact: The capsomeres are arranged in 20 equilateral triangles in icosahedral viruses.