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GATE 2020 BT Q.32: solution and answer

GATE 2020 · BTQ.32 · 2 marks · MCQ

Some of the cytokinins used in plant tissue culture media are given below: [P] BAP, [Q] Zeatin, [R] Kinetin, [S] 2iP. Which of these are synthetic analogs?

  1. (A)

    P and Q only

  2. (B)

    Q and S only

  3. (C)

    R and S only

  4. (D)

    P and R only

See the question in the paper
GATE 2020 BT question 32Tap to open full size

Answer and solution

ANSWER

The synthetic cytokinin analogs are BAP and kinetin, so the answer is (D) P and R only.

Official answer: DSource: Official answer key, GATE 2020 BT (IIT Delhi)

  1. Cytokinins are adenine derivatives. Natural cytokinins are made by plants and carry an isoprenoid side chain on the position of adenine. Synthetic analogs are made in the laboratory and are not regular plant products.

  2. [Q] Zeatin is a natural cytokinin, first isolated from immature maize (Zea mays) kernels. It is not synthetic, so options A and B, which contain Q, are wrong.

  3. [S] 2iP (-isopentenyladenine) is a natural cytokinin with an isoprenoid side chain. It is the parent of the natural isoprenoid cytokinins, so it is not synthetic. Option C, which contains S, is wrong.

  4. [P] BAP (6-benzylaminopurine) has a benzyl side chain instead of an isoprenoid one. It is a synthetic analog.

  5. [R] Kinetin (6-furfurylaminopurine) was first obtained as a breakdown product of heat-treated DNA. It is treated as a synthetic cytokinin and is not a regular plant hormone.

  6. The synthetic analogs are therefore P (BAP) and R (kinetin), which is option D.

KEY IDEA

Natural cytokinins (zeatin, 2iP) have an isoprenoid side chain on the of adenine. Synthetic ones (BAP, kinetin) have an aromatic side chain (benzyl, furfuryl) instead.

WATCH OUT FOR

Treating kinetin as natural because it is an adenine derivative with a cytokinin effect, or treating 2iP as synthetic because it is often added to media as a bought chemical. What counts is whether plants make it naturally.

From the GATE 2020 BT paper. Every question of this paper · Download the full paper · All 8 Plant tissue culture questions, with notes

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