All Free Biology MCQs with Answers

2861. HIV belongs to which group of viruses?

• A. DNA virus
• B. DNA enveloped virus
• C. Protein tumor virus
• D. Retrovirus

Explanation: HIV (Human Immunodeficiency Virus) is an RNA virus that uses reverse transcriptase to convert its RNA into DNA inside host cells.This ability to reverse the normal flow of genetic information (RNA → DNA) classifies it as a retrovirus.

2862. In how many stages is the HIV infection process divided?

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: HIV progresses through three main stages: an early phase where the person carries the virus without clear symptoms, a middle phase marked by mild illnesses and immune weakness, and a final phase where the immune system is severely damaged and full-blown AIDS develops.

2863. Which of the following is a viral sexually transmitted disease?

• A. Dengue
• B. Genital Herpes
• C. Gonorrhea
• D. Syphilis

Explanation: Genital herpes is an STI that develops when someone becomes infected with the Herpes Simplex Virus, usually HSV-2 and sometimes HSV-1. The virus enters through small breaks in the skin or mucosa during sexual contact and establishes a lifelong infection. Once it's in the body, it can stay dormant in nerve cells and reactivate from time to time, causing outbreaks of painful sores or sometimes no symptoms at all.

2864. In AIDS, "D" stands for:

• A. Different
• B. Difficult
• C. Deficiency
• D. Degenerate

Explanation: The abbreviation of AIDS is Acquired Immune Deficiency Syndrome, so D in AIDS stands for deficiency. Thus option C is the correct option.

2865. Virus is a latin word meaning:

• A. Sweet
• B. Sour
• C. Poison
• D. Toxic
• E. Acidic

Explanation: In Latin, virus means poison/ slimy liquid. It is a substance which is capable of infecting others.

2866. What does the term bacteriophage refer to?

• A. A virus that infects bacteria
• B. A bacterium that infects virus
• C. A virus which behaves as bacteria
• D. Combination of Bacterium & Virion

Explanation: A bacteriophage is a type of virus that specifically infects bacteria. It attaches to the surface of bacterial cells and injects its genetic material into the host, taking over the bacterial machinery to replicate itself.

2867. How many tail fibrils are attached to the end plate of a bacteriophage?

• A. 2
• B. 4
• C. 6
• D. 8

Explanation: Bacteriophages typically have tail fibers attached to the end plate. These tail fibers help the phage attach to specific receptors on the surface of the bacterial host cell. There are six long tail fibers attached to the end plate of a bacteriophage.

2868. The enzymes integrase, protease, and reverse transcriptase are found in which virus?

• A. Hepatitis A virus
• B. Herpes virus
• C. Influenza virus
• D. Human immunodeficiency virus

Explanation: Human immunodeficiency virus (HIV) is a retrovirus, and it contains integrase, protease, and reverse transcriptase enzymes. Integrase helps integrate viral DNA into the host cell genome, protease cleaves viral polyproteins to produce functional viral proteins, and reverse transcriptase synthesizes DNA from the viral RNA genome.

2869. Which one of the following is not a characteristic of viruses?

• A. They do not respire
• B. They do not excrete
• C. They do not have the ability to reproduce
• D. They can be crystallised

Explanation: Viruses are acellular, obligate, intracellular parasites. Viruses are not alive, because they do not complete all of the seven life processes: Movement, Respiration, Sensitivity, Nutrition, Excretion, Reproduction, and Growth. The only property of life they exhibit is replication.

2870. In 1935 W.M. Stanley prepared an extract of:

• A. Tobacco mosaic virus (TMV)
• B. Human immunodeficiency virus (HIV)
• C. Flu virus
• D. Polio virus

Explanation: Wendell Stanley studied the tobacco mosaic virus, which attacks the leaves of tobacco plants. From considerable quantities of infected tobacco leaves, he succeeded in extracting the virus in the form of pure crystals in 1935.