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Health and disease, immunity, cancer, HIV/AIDS and substance abuse: NEET MCQs with answers

142 questions on this topic of Biology and Human Welfare (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. An intestinal parasite that is monoxenous (requiring only one host) and causes internal bleeding, muscular pain, blockage of the intestinal passage, and anaemia is:

  1. Wuchereria bancrofti
  2. Taenia solium
  3. Entamoeba histolytica
  4. Ascaris lumbricoides
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Answer: (D) Ascaris lumbricoides

Ascaris lumbricoides is an intestinal roundworm causing ascariasis. Symptoms include internal bleeding, muscular pain, fever, anaemia, and obstruction of the intestinal passage; it completes its life cycle in a single host (human).

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2. Graft rejection during organ transplantation is mainly due to:

  1. Humoral immune response only
  2. Cell-mediated immune response (T-lymphocytes)
  3. Innate immunity only
  4. Interferons
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Answer: (B) Cell-mediated immune response (T-lymphocytes)

The body can differentiate 'self' and 'non-self'; cell-mediated immunity is responsible for graft rejection, so tissue and blood group matching are essential before transplant.

hard

3. Assertion (A): A person who has recovered from measles is usually protected for life. Reason (R): Acquired immunity has memory, producing a highly intensified secondary response on later exposure. Choose the correct option.

  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is not the correct explanation of A
  3. A is true but R is false
  4. A is false but R is true
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Answer: (A) Both A and R are true and R is the correct explanation of A

Memory B and T cells formed during the first infection give a rapid, intense secondary response, preventing disease on re-exposure.

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4. In the mosquito, the sporozoites of Plasmodium are stored in the:

  1. Stomach
  2. Salivary glands
  3. Ovaries
  4. Malpighian tubules
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Answer: (B) Salivary glands

After fertilisation and development in the mosquito's stomach wall, sporozoites migrate to and are stored in the salivary glands, from where they are injected into humans.

easy

5. Which of the following infectious diseases is transmitted from person to person via the bite of an infected female Aedes mosquito?

  1. Filariasis
  2. Chikungunya
  3. Amoebiasis
  4. Pneumonia
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Answer: (B) Chikungunya

Chikungunya and dengue are transmitted to humans through the bites of female Aedes mosquitoes. Filariasis is spread by Culex mosquitoes, while amoebiasis is water/food-borne and pneumonia is airborne via droplets.

hard

6. The thymus is quite large at the time of birth, but:

  1. Is replaced by the spleen in adults
  2. Keeps increasing throughout life
  3. Disappears at birth
  4. Keeps reducing in size with age, and by puberty it attains a very small size
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Answer: (D) Keeps reducing in size with age, and by puberty it attains a very small size

The thymus is large at birth and reduces with age; it provides the micro-environment for the development and maturation of T-lymphocytes.

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7. After entering the human body, HIV first enters macrophages, where:

  1. RNA is replicated to form viral DNA with the help of reverse transcriptase
  2. It produces antibodies
  3. It forms spores
  4. It is destroyed immediately
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Answer: (A) RNA is replicated to form viral DNA with the help of reverse transcriptase

In macrophages, viral RNA is copied into viral DNA by reverse transcriptase and incorporated into host DNA. Macrophages continue to produce virus, acting like an HIV factory.

NCERT Class 12

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8. During the lifecycle of Plasmodium vivax in the human host, synchronous rupturing of infected erythrocytes occurs. Which specific event is directly responsible for triggering the characteristic chill and high recurring fever?

  1. Release of sporozoites directly from ruptured hepatocyte membranes
  2. Fusion of microgametes and macrogametes within human circulatory capillaries
  3. Engulfment of salivary gland secretions containing anticoagulant by dendritic cells
  4. Lysis of erythrocytes releasing merozoites along with the toxic pigment hemozoin
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Answer: (D) Lysis of erythrocytes releasing merozoites along with the toxic pigment hemozoin

The rupture of red blood cells (erythrocytes) releases merozoites together with a toxic product called hemozoin. The presence of free hemozoin in the bloodstream induces chills and periodic high fever every 3 to 4 days.

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9. The hepatitis B vaccine produced from yeast is an example of:

  1. Passive immunisation
  2. A live attenuated vaccine from patients
  3. A vaccine produced using recombinant DNA technology
  4. Antitoxin therapy
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Answer: (C) A vaccine produced using recombinant DNA technology

Recombinant DNA technology allows antigenic polypeptides of pathogens to be produced in bacteria or yeast, as with the hepatitis B vaccine from yeast.

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10. Match Column-I with Column-II. Column-I: (A) Typhoid (B) Malaria (C) Amoebiasis (D) Elephantiasis Column-II: (i) Entamoeba histolytica (ii) Wuchereria bancrofti (iii) Salmonella typhi (iv) Plasmodium vivax

  1. A-(iii), B-(iv), C-(i), D-(ii)
  2. A-(iv), B-(iii), C-(i), D-(ii)
  3. A-(iii), B-(i), C-(iv), D-(ii)
  4. A-(ii), B-(iv), C-(i), D-(iii)
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Answer: (A) A-(iii), B-(iv), C-(i), D-(ii)

Typhoid — Salmonella typhi; malaria — Plasmodium; amoebiasis — Entamoeba histolytica; elephantiasis — Wuchereria.

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11. Typhoid fever in humans is caused by Salmonella typhi, which enters the small intestine through food and water. Typhoid fever can be confirmed by the:

  1. Mantoux test
  2. ELISA test
  3. Biopsy
  4. Widal test
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Answer: (D) Widal test

Sustained high fever (39–40 °C), weakness, stomach pain, constipation, headache and loss of appetite are symptoms; typhoid is confirmed by the Widal test.

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12. The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The antibodies produced in allergy are of the type:

  1. IgM
  2. IgA
  3. IgG
  4. IgE
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Answer: (D) IgE

Allergens such as dust mites, pollens and animal dander stimulate IgE antibodies; mast cells then release chemicals like histamine and serotonin.

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