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GATE 2025 BT Q.52: solution and answer

GATE 2025 · BTQ.52 · 2 marks · MSQ

Which of the following statements is/are true about telomerase?

  1. (A)

    Telomerase has 5'-3' DNA-dependent DNA polymerisation activity

  2. (B)

    Telomerase has 5'-3' RNA-dependent DNA polymerisation activity

  3. (C)

    Telomerase contains an RNA subunit

  4. (D)

    Telomerase has 3'-5' DNA-dependent DNA polymerisation activity

See the question in the paper
GATE 2025 BT question 52Tap to open full size

Answer and solution

ANSWER

Telomerase acts as an RNA-dependent DNA polymerase (reverse transcriptase) and is a ribonucleoprotein enzyme, so both (B) and (C) are true.

Official answer: B, CSource: Official answer key, GATE 2025 BT (IIT Roorkee)

  1. Telomerase is a ribonucleoprotein enzyme composed of a catalytic protein subunit (TERT) and an integral RNA subunit (TERC/TR) that serves as the template for synthesising telomeric repeats — this makes statement (C) true.

  2. Telomerase synthesises new telomeric DNA in the 5'\to3' direction using its own internal RNA (not a DNA template) as the template, i.e. it is a specialised reverse transcriptase with RNA-dependent DNA polymerase activity — this makes statement (B) true.

  3. Statement (A) is false: telomerase does not copy a DNA template, so it has no DNA-dependent DNA polymerase activity.

  4. Statement (D) is false on two counts: telomerase synthesises DNA only 5'\to3' (like every known polymerase, never 3'\to5'), and its template is RNA, not DNA.

  5. Since the question is an MSQ, all true statements must be selected: (B) and (C).

KEY IDEA

Telomerase is a ribonucleoprotein reverse transcriptase: its RNA subunit (TERC) is the template it copies, and its protein subunit (TERT) extends chromosome ends 5'\to3' using that RNA template — i.e. RNA-dependent DNA polymerase activity.

WATCH OUT FOR

Confusing telomerase with a standard DNA-dependent DNA polymerase (choosing A) because both "make DNA", while missing that telomerase's template is its own RNA, not a DNA strand — and forgetting that all polymerases (including telomerase) synthesise only 5'\to3', which rules out D on direction alone even before considering the template type.

From the GATE 2025 BT paper. Every question of this paper · Download the full paper · All 21 Gene expression questions, with notes

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