All Free Biology MCQs with Answers

3051. Which of the following is not true for virions?

• A. Reproduce independently
• B. Contain DNA
• C. Contain RNA
• D. Extracellular

Explanation: Virions, which are individual virus particles, do not reproduce independently. Viruses are obligate intracellular parasites, meaning they require a host cell to replicate and reproduce. The virion itself is essentially the extracellular form of a virus, consisting of genetic material (either DNA or RNA) surrounded by a protein coat called a capsid.

3052. What is the approximate diameter of a retrovirus?

• A. 150 nm
• B. 100 nm
• C. 200 nm
• D. 250 nm

Explanation: The diameter of retroviruses typically ranges from approximately 80 to 120 nanometers (nm). Retroviruses are a family of enveloped viruses characterized by their use of reverse transcriptase to convert their RNA genome into DNA upon entering host cells. The viral particles consist of an outer lipid envelope, viral glycoproteins, and an inner core containing the RNA genome and viral enzymes. The size of retroviruses can vary slightly depending on the specific type of retrovirus.

3053. 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.

3054. 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.

3055. 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.

3056. 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.

3057. 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.

3058. 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.

3059. 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.

3060. 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.