All Free Biology MCQs with Answers

2731. Reverse transcriptase can convert:

• A. Single-stranded RNA genome into single-stranded DNA
• B. Single-stranded RNA genome into double-stranded DNA
• C. Double-stranded DNA genome into single-stranded RNA
• D. Double-stranded DNA genome into double-stranded RNA

Explanation: Reverse transcriptase is a key enzyme in certain viruses, such as retroviruses, which include HIV. It allows these viruses to replicate their RNA genome into DNA and integrate it into the host cell's genome. This conversion is crucial for the virus's life cycle and is an essential step in retroviral replication.

2732. The double-stranded viral DNA can be incorporated into the host T4 genome as a:

• A. Prophage
• B. Provirus
• C. Bacteriophage
• D. Phage virus

Explanation: A prophage is a phage DNA that has been integrated into the DNA of a bacterial host cell. This is a common phenomenon in bacterial viruses like the T4 bacteriophage. The viral DNA becomes a part of the host cell's genome and remains dormant within the host until certain conditions trigger its activation and subsequent replication, leading to the lytic cycle where new phage particles are produced and released.

2733. AIDS was reported by some physicians in the early 1980s in young homosexual males. They showed the following symptoms, EXCEPT:

• A. Severe pneumonia and a rare vascular cancer
• B. Rare pneumonia and severe vascular cancer
• C. Sudden weight loss and swollen lymph nodes
• D. Swollen lymph nodes and general loss of immune functions

Explanation: These symptoms were present in individuals with AIDS during its early recognition. The disease was initially identified in the early 1980s primarily in young homosexual males, and it presented with various symptoms including those listed in the incorrect options. Over time, it became clear that AIDS was caused by the human immunodeficiency virus (HIV) and that it could affect individuals regardless of their sexual orientation.

2734. Human immunodeficiency virus (HIV) causes:

• A. Severe combined immunodeficiency syndrome
• B. Acquired immunodeficiency syndrome
• C. Non-Hodgkin's lymphoma
• D. Bubble boy disease

Explanation: HIV is a virus that attacks the immune system. It can eventually lead to AIDS (acquired immunodeficiency syndrome), which is a condition in which the immune system is so weak that it cannot fight off infections.

2735. Recent studies on HIV reveal that the virus infects and multiplies but does not cause disease in them.

• A. Heterosexual males
• B. Young homosexual males
• C. Monkeys
• D. Young homosexual females

Explanation: Recent studies of HIV reveal that the virus infects and multiplies in monkeys but does not cause disease in them which means that HIV is host specific.

2736. Following are the means of transmission of AIDS, EXCEPT:

• A. Intimate sexual contact and breastfeeding
• B. Use of common syringes and surgical instruments
• C. Blood transfusion without screening
• D. Human immunodeficiency virus

Explanation: AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV). The virus attacks the immune system and weakens it, making the body susceptible to various infections and diseases. However, the virus itself is not a means of transmission, it is the cause.

2737. The most important measure to prevent AIDS and HIV is:

• A. Avoiding intravenous drugs
• B. Avoiding intracellular drugs
• C. Avoiding use of syringes
• D. Avoiding the direct contact with HIV

Explanation: This is the most important and accurate measure. HIV is primarily transmitted through direct contact with certain body fluids, including blood, semen, vaginal fluids, rectal fluids, and breast milk, from a person who is already infected with HIV. By avoiding direct contact with these fluids, the risk of HIV transmission can be significantly reduced.

2738. Which of the following are of viral origin?

• A. 1,2,3,4
• B. 1,2,3,5
• C. 2,3,4,5
• D. 1,2,4,5

Explanation: Answer is "1,2,3,5"Explanation: Other than envelop which have been derived from the cell membrane of host cell, rest of the all parts of virus are genetically encoded on viral (HIV) genome.

2739. Which one of the following is not of viral origin?

• A. 2
• B. 3
• C. 4
• D. 5

Explanation: Answer is "4"Explanation: Envelope have been labeled by 4. It is part of the plasma membrane of host cell and its genetic information is not located on the viral genome.

2740. Which of the following is viral envelope?

• A. 2
• B. 3
• C. 4
• D. 5

Explanation: Answer is "4"Take a look at the diagram.