Free Acellular Life MCQs with Answers

41. A positive ELISA screening result for HIV is usually confirmed by

• A. repeating the ELISA only
• B. the Western blot technique
• C. a blood culture on agar
• D. a chest X ray

Explanation: ELISA is sensitive but can give false positives, so Western blot, which separates the viral proteins and shows which antibodies are present, is used to confirm. Viruses cannot be cultured on ordinary agar, ruling that option out entirely.

42. A mother infected with HIV can pass the virus to her child

• A. during pregnancy, during delivery and through breastfeeding
• B. only through the genes she passes on
• C. only if the child is vaccinated
• D. never, since HIV requires a needle to spread

Explanation: Mother to child transmission can occur across the placenta, at birth and in breast milk, which is why antiretroviral treatment during pregnancy sharply cuts the risk. HIV is never inherited through genes, since it infects cells rather than the germ line.

43. Which everyday contact does NOT transmit HIV?

• A. Sharing needles contaminated with infected blood
• B. Sexual contact with an infected person
• C. Transfusion of infected blood
• D. Sharing a meal with an infected person

Explanation: HIV needs direct access to blood or mucous membranes, so casual contact such as meals, handshakes and sneezing carries no risk. Knowing this is essential both for prevention and for ending the isolation of infected people.

44. Combination antiretroviral therapy uses several drugs at the same time because

• A. single drugs are too expensive to manufacture
• B. the drugs increase each other's side effects
• C. HIV develops resistance rapidly to any single drug
• D. they kill the virus directly by oxidation

Explanation: HIV mutates so fast that a population resistant to one drug soon appears, but becoming resistant to three at once is far harder. That is why cocktail therapy suppresses the virus for years even though it cannot eliminate the provirus.

45. HIV is classified within which subgroup of retroviruses?

• A. Oncoviruses
• B. Lentiviruses
• C. Spumaviruses
• D. Adenoviruses

Explanation: Lentiviruses, meaning slow viruses, cause long incubation, persistent infections, which fits HIV's years long course from infection to AIDS. Oncoviruses cause cancers and adenoviruses are DNA viruses, so neither group contains HIV.

46. Blood banks test every donated unit of blood for HIV primarily to

• A. prevent transmission of the virus through transfusion
• B. increase the storage life of the blood
• C. raise the red cell count of the unit
• D. detect anaemia in the donor

Explanation: One unit of infected blood can transmit HIV directly into the recipient's circulation, so screening donated blood is one of the most effective barriers to spread. The tests used have nothing to do with storage or cell counts.

47. The envelope glycoprotein gp120 of HIV is important because it

• A. makes vaccination unnecessary
• B. destroys the host's red blood cells
• C. binds to receptors on host cells and allows the virus to enter
• D. makes the virus resistant to heat

Explanation: gp120 projects from the envelope and locks onto CD4 receptors, the first step of infection, which is why it is also the main target researchers aim antibodies at. It has no role against heat or red cells.

48. Which statement about HIV is correct?

• A. It can be cured with a course of antibiotics
• B. It survives for weeks on dry surfaces
• C. It is commonly spread by mosquito bites
• D. It destroys helper T cells and progressively weakens immunity

Explanation: HIV replicates inside helper T lymphocytes and destroys them, so immunity collapses and opportunistic infections follow. Antibiotics cannot touch a virus, the virus dies quickly outside the body, and mosquitoes do not transmit it.

49. Why are retroviruses placed in a separate class of RNA viruses?

• A. They always infect animal cells only
• B. Their RNA acts directly as mRNA
• C. They lack protein coats
• D. They use reverse transcriptase to make DNA from RNA

Explanation: A retrovirus reverses the usual flow of information by copying its RNA genome into DNA, which integrase then inserts into the host chromosome as a provirus, and that integration is why HIV infection is lifelong. In other RNA viruses the genome often does act directly as messenger RNA, which is the contrast the second option draws. Retroviruses have perfectly ordinary capsids and envelopes.