Free Biodiversity and Variety of Life MCQs with Answers

2661. Viruses may not replicate in:

• A. Blood Plasma
• B. Plant cell
• C. Skin cell
• D. Hepatocytes

Explanation: Viruses are obligate intracellular parasites, meaning they require a host cells machinery to replicate and produce new viral particies. Blood plasma is the liquid component of blood. that does not contain any blood cells, such as red blood cells. white blood cells, or platelets. Since blood plasma lacks the necessary host cells for viral reproduction, viruses cannot replicate in blood plasma.

2662. Volume of bacteriophage is about _ of host.

• A. 1/10 times
• B. 1/100 times
• C. 1/10,000 times
• D. 1/1000 times

Explanation: The volume of a bacteriophage is about 1/1000th the volume of its host.

2663. Hepatitis C is also known as:

• A. Infections Hepatitis
• B. Serum Hepatitis
• C. Infusion Hepatitis
• D. Delta Hepatitis

Explanation: Hepatitis C virus is RNA enveloped virus that causes infusion hepatitis.

2664. Rabies is caused by:

• A. Paramyxovirus
• B. Rhinovirus
• C. Arbovirus
• D. Rhabdovirus
• E. Poliovirus

Explanation: Rabies is a viral disease that affects the central nervous system and is caused by the Rhabdovirus. The specific virus responsible for rabies is called the Rabies lyssavirus, which belongs to the family Rhabdoviridae.

2665. Hepatitis is caused by:

• A. Protozoans
• B. Algae
• C. Bacteria
• D. Fungi
• E. Virus

Explanation: Hepatitis is an inflammation of the liver, and it can be caused by several factors, including viral infections. The most common types of hepatitis are caused by viruses, specifically hepatitis A, hepatitis B, hepatitis C, hepatitis D, and hepatitis E viruses. Therefore the correct option is E.

2666. At which stage of HIV infection does one usually show symptoms of AIDS?

• A. Within 15 days of sexual contact with an infected person
• B. When the infected retrovirus enters host cells
• C. When HIV damages a large number of helper T-lymphocytes
• D. When the viral DNA is produced by reverse transcriptase

Explanation: AIDS is a condition that arises when the immune system is severely compromised due to a significant reduction in CD4 cells, which are targeted by the HIV virus. HIV initially infects the host by entering cells and using its reverse transcriptase to integrate its genetic material into the host's DNA. Over time, as the number of helper T-lymphocytes (CD4 cells) is depleted, the immune system weakens, leading to the symptoms associated with AIDS. This progressive damage does not occur immediately after infection or at the initial entry of the virus into cells, but rather after a significant loss of CD4 cells.

2667. HIV, which causes AIDS, first starts destroying:

• A. Helper T-Lymphocytes
• B. B-lymphocytes
• C. Leukocytes
• D. None of these

Explanation: AIDS (acquired immunodeficiency syndrome), a syndrome, is caused by the retrovirus HIV (human immunodeficiency virus). The virus destroys a subgroup of lymphocytes, the helper T cells (or CD4 lymphocytes), resulting in suppression of the body's immune response. HIV is transmitted in blood, semen, and vaginal fluid; the major routes of infection are unprotected vaginal and anal intercourse, intravenous drug abuse, and the administration of contaminated blood and blood products. A combination of antiviral drugs can delay the development of full-blown AIDS for many years but cannot fully cure the disease.

2668. Which of the following pairs of diseases is caused by a virus?

• A. Rabies, Mumps
• B. Cholera, Tuberculosis
• C. Typhoid, Tetanus
• D. AIDS, Syphilis

Explanation: Mumps is an infectious disease that causes fever, difficulty in opening the mouth, and painful swelling of the parotid glands, which lie just below the earlobes. It is caused by a paramyxovirus, which is present in the saliva of the infected person. Rabies (hydrophobia) is caused by a virus named the rabies virus. It is introduced into the body through the bite of rabid (mad) dogs. The most important characteristic symptom of this disease is the fear of water.

2669. Viruses have?

• A. DNA is enclosed in a protein coat
• B. Prokaryotic nucleus
• C. Single chromosome
• D. Both DNA and RNA

Explanation: The most accurate statement about viruses is that they contain genetic material (either DNA or RNA) enclosed in a protein coat, and they lack a prokaryotic or eukaryotic nucleus. Viruses are nucleoprotein entities that can utilize the synthetic machinery of a living cell of the host organism for their multiplication, which does not involve growth and division. They have either RNA or DNA as genetic material and a protein coat.

2670. Which of the following statements is not true for retroviruses?

• A. DNA is not present at any stage in the life cycle of retroviruses
• B. Retroviruses carry a gene for RNA-dependent DNA polymerase
• C. The genetic material in mature retroviruses is RNA
• D. Retroviruses are causative agents for certain kinds of cancer in humans

Explanation: Retroviruses are unique viruses with a complex life cycle, and their features help explain which statements are true or false. Statement (a) is false because retroviruses indeed have a DNA stage in their replication cycle. After infection, they use the enzyme reverse transcriptase to convert their RNA genome into DNA, which integrates into the host cell's chromosomes. Statement (b) is true because retroviruses encode RNA-dependent DNA polymerase, better known as reverse transcriptase, which is essential for converting viral RNA into DNA. Statement (c) is also true since retroviruses carry RNA as their genetic material inside mature virions, which is used as a template after infection. Finally, statement (d) is true because some retroviruses, such as HTLV-1, are oncogenic, meaning they can disrupt normal host cell growth regulation and potentially cause cancers like adult T-cell leukaemia. These features distinguish retroviruses from other types of viruses.