All Free Biology MCQs with Answers

2441. Identify the site where Wuchereria bancrofti is normally found in the human body:

• A. Muscles of the legs
• B. Blood vessels of the thigh region
• C. Skin between the fingers
• D. Lymphatic vessels of the lower limbs

Explanation: Wuchereria bancrofti is a dreaded human parasite. It is a digenetic parasite completing its life cycle in two hosts the final host is man harboring the adult worm. The disease passes through four stages in human beings: In the first stage, the patient has increased eosinophils, and enlarged lymph nodes. The second or carrier stage is symptomless. The third stage is characterized by filarial fever, inflammation of lymph nodes (lymphadenitis) and lymph vessels (lymphangiectasis), and reversible lymphoedema(excess fluid in tissues due to 387 obstruction of lymph vessels) in various body parts. The fourth or final stage is manifested by lymphoedema accompanied by thickening of subcutaneous tissues and skin so that there is permanent swelling mostly of feet, legs, thighs, scrotal sacs, breast, etc. It is called elephantiasis.

2442. Which one of the following is a hallucinogenic drug?

• A. Caffeine
• B. Morphine
• C. Lysergic acid diethylamide
• D. Opium

Explanation: LSD is a psychedelic drug since it causes optical and auditory hallucinations and induces behavioral abnormalities. Opium and morphine are opiate narcotics that suppress brain activity and relieve pain. Caffeine is a stimulant that temporarily stimulates the nervous system. Lysergic acid diethylamide, commonly known as LSD, is a potent hallucinogenic drug.

2443. Motile zygote of Plasmodium occurs in:

• A. Gut of female Anopheles
• B. Salivary glands of Anopheles
• C. Human RBCs
• D. Human liver

Explanation: Plasmodium, a tiny protozoan parasite causes malaria in humans and is transmitted through the bite of an infected female Anopheles mosquito. When female Anopheles sucks the blood of an infected human it takes up gametocytes (sexual stages of parasite) with blood meal. The gametocytes come out of the RBCs into the lumen(cavity) of the stomach of the mosquito. In the stomach, the male gametocyte divides and forms 6 to 8 long, motile, whiplike microgametes(male gametes). The female gametocyte does not divide but undergoes a process of maturation to become the macrogamete(female gamete). A microgamete penetrates a macrogamete and fertilization(syngamy) takes place, resulting in the formation of a zygote. The zygote elongates and becomes a worm-like motile organism called an ookinete. Ookinete further changes into sporozoites(mature infective stage of Plasmodium).

2444. Which one of the following is not a property of cancerous cells whereas the remaining three are?

• A. They compete with normal cells for vital nutrients
• B. They do not remain confined in the area of formation
• C. They divide in an uncontrolled manner
• D. They show contact inhibition

Explanation: Contact inhibition is a property of normal cells by virtue of which contact withother cells inhibits their uncontrolled growth. Cancerous cells lack this property. One of the hallmarks of cancer is the loss of contact inhibition not gain of it. Cancer cells often ignore the signals from neighboring cells and continue to divide and grow uncontrollably, leading to the formation of tumors. This loss of contact inhibition is a crucial aspect of cancer development and progression.

2445. Cirrhosis of liver is caused by the chronic intake of:

• A. Opium
• B. Alcohol
• C. Tobacco(chewing)
• D. Cocaine

Explanation: Cirrhosis is a condition in which the liver responds to injury or death of some of its cells by producing interlacing strands of fibrous tissue between which are nodules o regenerating cells. The liver becomes tawny and characteristically knobbly(due to the nodules). One of the causes include alcoholism(alcoholic cirrhosis). Chronic infection with hepatitis B or hepatitis C viruses can lead to liver inflammation and fibrosis, eventually progressing to cirrhosis.

2446. Where will you look for the sporozoites of the malarial parasite?

• A. Saliva of infected female Anopheles mosquito
• B. Red blood corpuscles of human suffering from malaria
• C. Spleen of infected humans
• D. Salivary glands of freshy moulted female Anopheles mosquito

Explanation: Sporozoites represent the infective forms of malarial parasites. A healthy person acquires infection, when a female Anopheles mosquito, containing sporozoites, bites the person for sucking his blood. The mosquito punctures the host's skin by its proboscis and first introduces some saliva into the bloodstream. Along with saliva, thousands of sporozoites are inoculated in the host. The motile zygote then undergoes further development in the mosquito's gut to produce sporozoites, which migrate to the mosquito's salivary glands.

2447. Common cold is not cured by antibiotics because it is:

• A. Caused by a virus
• B. Caused by a Gram positive bacterium
• C. Caused by a Gram negative bacterium
• D. Not an infectious disease

Explanation: Common cold is caused by some 100 types of Rhinoviruses. It is one of the most common infectious diseases in humans. Antibiotics are substances that destroy or inhibit the growth of microorganisms, particularly disease-producing bacteria and fungi. Antibiotics are obtained from microorganisms(especially molds) or synthesized. Many antibiotics interfere with the pathogen protein synthesis. Some (e.g. Penicillin) prevent cross-linking of the glycan chains of peptidoglycan molecules in bacterial cell walls. Since the viruses do not possess cell walls and their own protein-synthesizing apparatus, antibiotics do not attack them.

2448. Ringworm in humans is caused by:

• A. Bacteria
• B. Fungi
• C. Nematodes
• D. Viruses

Explanation: Ringworm (tinea) is a fungal infection of the skin, the scalp, or the ails. Ringworm is caused by the dermatophyte fungi species of Microsporum, trichophyton, and epidermophyton ringworms and also affects animals, a source of infection for humans. It can be spread by direct contact or via infected materials. The lesions of ringworm may form partial or complete rings and may cause intense itching. The disease is treated with antifungal agents taken by mouth or applied locally. These fungi can infect the skin, hair, and nails, leading to the development of ringworm, also known as dermatophytosis.

2449. Widal test is used for the diagnosis of:

• A. Malaria
• B. Pneumonia
• C. Tuberculosis
• D. Typhoid.

Explanation: Widal test (developed by G.F.I Widal) is an agglutination test for the presence of antibodies against the Salmonella organism that causes typhoid fever. It is used to diagnose the presence of the disease in a patient. If the patient has been exposed to Salmonella bacteria and has developed antibodies against them, a reaction called agglutination occurs. Agglutination causes the clumping together of the bacterial antigens and antibodies in the test solution, which is visible to the laboratory technician.

2450. Infectious protein are present in:

• A. Gemini viruses
• B. Prions
• C. Viroids
• D. Satellite viruses.

Explanation: Prions are named by Stanley Prusiner (who got the Nobel Prize in 1997). Prions are infectious agents which are made of proteins only(without nucleic acid). Prions are the causal agents of scrapie disease of sheep. Prion diseases are a unique and challenging category of infectious diseases due to their unconventional nature and lack of traditional genetic material. They continue to be a subject of scientific research to better understand their mechanisms and develop potential treatments.