All Free Biology MCQs with Answers

2491. The blood cancer is known as:

• A. Haemolysis
• B. Haemophilia
• C. Leukaemia
• D. Thrombosis

Explanation: The normal white blood cell (WBC) count ranges from 5,000 to 10,000 per cubic millimeter of blood. Leukemia, or blood cancer, is characterized by an abnormal increase in the WBC count, typically ranging from 20,000 to 1,000,000/mm3 due to their excessive production in the bone marrow. Hemolysis refers to the breakdown of red blood cells (RBCs). Hemophilia is a condition in which blood clots slowly, while thrombosis is the formation of blood clots inside blood vessels.

2492. Which one of the following pairs is not correctly matched?

• A. Syphilis; Trichuris trichiura
• B. Sleeping sickness; Trypanosoma gambiense
• C. Dengue fever; Arbovirus
• D. Plague; Yersinia pestis

Explanation: Syphilis is caused by a spirochete (spiral bacterium) called Treponema pallidum. Sleeping sickness is a disease found in tropical Africa and is caused by the presence of the parasitic protozoan Trypanosoma gambiense. Plague is an epidemic disease in rats, which is transmitted to humans by rat fleas. Dengue is a disease transmitted to humans by mosquitoes, specifically Aedes aegypti.

2493. Which one of the following diseases is due to an allergic reaction?

• A. Enteric fever
• B. Skin cancer
• C. Goitre
• D. Hay fever

Explanation: Hay fever is an allergic reaction to the pollen of grasses, trees, and other plants. It is characterized by inflammation of the membrane lining the nose and sometimes the conjunctiva. The symptoms, including sneezing, a runny or blocked nose, and watering eyes, are a result of histamine released by mast cells.

2494. Which of the following causes plague?

• A. Trichinella spiralis
• B. Salmonella typhimuium
• C. Yersinia pestis
• D. Leishmania donovani

Explanation: Plague is an acute epidemic disease of rats and other wild rodents caused by the bacterium Yersinia pestis. It is transmitted to humans by rat fleas. The symptoms include headache, fever, weakness, aching limbs, and delirium, followed by acute painful swellings of the lymph nodes. Bleeding under the skin, resulting in black patches, can lead to ulcers, which may prove fatal. Treatment with tetracycline, streptomycin, and chloramphenicol is effective.Trichinosis is caused by Trichinella spiralis, which lives as an endoparasite in the human intestine. Salmonella typhimurium causes enteric fevers, and Leishmania donovani is responsible for kalaazar.

2495. Antigens are present :

• A. Inside the cytoplasm
• B. On nuclear membrane
• C. Inside the nucleus
• D. On cell surface

Explanation: An antigen is any foreign substance, such as a protein or polysaccharide, present on the external coating of a pathogen, a component of vegetables, fruits, meats, drugs, chemicals, tissues, or organ transplants, which induces the immune system to produce antibodies.

2496. A cell coded protein that is formed in response to infection, with most animal viruses, is called :

• A. Histone
• B. Antibody
• C. Interferon
• D. Antigen

Explanation: Interferons are proteins that enhance a cell's resistance to viral attacks by unmasking genes responsible for synthesizing antiviral proteins. In humans, three groups of interferons have been discovered: 'a-interferons' from white blood cells, 'b-interferons' from connective tissue fibroblasts, and 'g-interferons' from lymphocytes.

2497. Which of the following correctly matches a sexually transmitted disease with its pathogen?

• A. Syphilis : Treponema pallidum
• B. Gonorrhoea : Entamoeba histolytica
• C. Urethritis : Bacillus anthracis
• D. Softsore : Bacillus brevis

Explanation: Syphilis is caused by a spirochete (spiral bacterium) Treponema pallidum. Gonorrhoea is caused by Neisseria gonorrhoea.Urethritis is inflammation of urethra.

2498. The main reason why antibodies could not solve all the problems of bacteria mediated disease was:

• A. Decreased efficiency of the immune system
• B. Insensitivity of the individual following prolonged exposure to antibiotics
• C. Development of mutant strains resistant to antibodies
• D. Inactivation of antibiotics by bacterial enzymes.

Explanation: Bacteria develop mutant strains that become resistant to antibodies, rendering these antibodies incapable of combating diseases mediated by bacteria.

2499. Which one engulfs pathogens rapidly?

• A. Acidophils
• B. Monocytes
• C. Basophils
• D. Neutrophils

Explanation: Neutrophils are the most abundant type of white blood cells and are an integral part of the immune system. These phagocytes are normally found in the bloodstream. However, during the acute phase of inflammation, particularly as a result of bacterial infection, neutrophils leave the vasculature and migrate toward the site of inflammation in a process called chemotaxis. They are the predominant cells in pus, accounting for its whitish/yellowish appearance. Neutrophils respond within an hour of tissue injury and are the hallmark of acute inflammation. Monocytes are also phagocytes, but they take approximately 78 hours to reach the site of injury. Acidophils and basophils are not phagocytic in nature.

2500. Analgesic drugs :

• A. Form tissues
• B. Relieve pain
• C. Relieve fatigue
• D. Cause pain

Explanation: An analgesic is a substance that reduces pain without causing unconsciousness, either by lowering the pain threshold or by increasing pain tolerance. There are several categories of analgesic drugs, including morphine and its derivatives, which produce analgesia by acting on the central nervous system; nonsteroidal anti-inflammatory drugs (e.g., aspirin); and local anesthetics.