IAE Academy

GATE 2020 BT Q.42: solution and answer

GATE 2020 · BTQ.42 · 2 marks · MCQ

Determine the correctness or otherwise of the following Assertion [a] and the Reason [r].

Assertion [a]: A genetically engineered rice that produces beta-carotene in the rice grain is called Golden rice

Reason [r]: Enabling biosynthesis of provitamin A in the rice endosperm gives a characteristic yellow/orange color

  1. (A)

    Both [a] and [r] are false

  2. (B)

    Both [a] and [r] are true but [r] is not the correct reason for [a]

  3. (C)

    Both [a] and [r] are true and [r] is the correct reason for [a]

  4. (D)

    [a] is true but [r] is false

See the question in the paper
GATE 2020 BT question 42Tap to open full size

Answer and solution

ANSWER

Option (C): both [a] and [r] are true, and [r] is the correct reason for [a].

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

  1. Assertion [a]. Rice endosperm normally lacks carotenoids. Rice engineered to make beta-carotene (provitamin A) in the grain is called Golden rice, so [a] is true.

  2. How it is engineered. A plant phytoene synthase gene (psy) and a bacterial phytoene desaturase gene (crtI) are introduced. Together with enzymes the endosperm already has, they complete the pathway from GGPP to phytoene, lycopene and then beta-carotene. The first version also carried a lycopene cyclase gene.

  3. Reason [r]. Beta-carotene is a carotenoid pigment that absorbs blue light, so grains that accumulate it look yellow to orange. Making provitamin A in the endosperm therefore does give a yellow/orange colour, so [r] is true.

  4. Link between [a] and [r]. The colour in [r] is the visible result of the carotenoid built up in [a], and it is the reason the rice is called 'Golden'. So [r] is the correct reason for [a].

  5. Options. (A) is wrong because both statements are true. (D) is wrong because [r] is true. (B) is wrong because [r] explains [a] and is not an unrelated fact.

  6. Both statements are true and [r] is the correct reason for [a], so the answer is option (C).

KEY IDEA

Golden rice is transgenic rice that makes beta-carotene (provitamin A) in the endosperm. The carotenoid pigment gives the grain its yellow/orange colour, which is where the name comes from.

WATCH OUT FOR

Treating the colour as a side detail and choosing (B). In this question the colour is the direct visible result of the carotenoid accumulation and explains the name.

From the GATE 2020 BT paper. Every question of this paper · Download the full paper · All 4 Transgenic plants questions, with notes

More Transgenic plants questions