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GATE 2019 BT Q.5: solution and answer

GATE 2019 · BTQ.5 · 1 mark · MCQ

Which one of the following enzymes is encoded by human immunodeficiency virus (HIV) genome?

  1. (A)

    Reverse transcriptase

  2. (B)

    Phospholipase

  3. (C)

    Phosphatase

  4. (D)

    ATP synthase

See the question in the paper
GATE 2019 BT question 5Tap to open full size

Answer and solution

ANSWER

The enzyme encoded by the HIV genome is reverse transcriptase, option (A).

Official answer: ASource: Official answer key, GATE 2019 BT (IIT Madras)

  1. HIV is a retrovirus with a single-stranded RNA genome. Its genome carries three major genes: gag (structural proteins), pol (enzymes) and env (envelope glycoproteins), plus regulatory and accessory genes.

  2. The pol gene encodes the viral enzymes reverse transcriptase, integrase and protease. Reverse transcriptase copies the viral RNA into DNA, which integrase inserts into the host genome. So (A) is encoded by the HIV genome.

  3. (B) Phospholipase is a lipid-hydrolysing enzyme made by host cells and some bacteria. The HIV genome has no gene for it, so it is wrong.

  4. (C) Phosphatase removes phosphate groups and is a host cell enzyme. The HIV genome has no gene for it, so it is wrong.

  5. (D) ATP synthase is a membrane enzyme of mitochondria, chloroplasts and bacteria. A virus has no energy-generating machinery and does not encode it, so it is wrong.

  6. Only reverse transcriptase is encoded by HIV, so the answer is (A).

KEY IDEA

HIV is a retrovirus. Its pol gene encodes reverse transcriptase, integrase and protease, and these are the enzymes the virus brings with it.

WATCH OUT FOR

Choosing a familiar host enzyme such as phosphatase or phospholipase. Viruses encode very few enzymes, and only those needed for their own replication cycle.

From the GATE 2019 BT paper. Every question of this paper · Download the full paper · All 11 Pathogens & antibiotics questions, with notes

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