3. In plant, if the sequence 5’-GATGGCACGAT-3’ is transcribe using opposite strand as template, the sequence of corresponding mRNA will be
(1) 5’-CUACCGUGCUA-3’
(2) 5’-GAUGGCACGAU-3’
(3) 5’-AUCGUGCCAUC-3’
(4) 5’ATGTCCATCAUA-3’

Correct Answer: (2) 5’-GAUGGCACGAU-3’

Explanation:

Step 1: Identify the Template Strand

• Given: 5’-GATGGCACGAT-3’

• This is the coding (non-template) strand, since transcription uses the opposite strand.

So the template strand is the complementary strand:

• Template DNA (3’ → 5’): 3’-CTACCGTGCTA-5’

Step 2: Transcribe into mRNA

Now transcribe using the template strand, replacing DNA bases with RNA bases:

So the mRNA sequence is:
5’-GAUGGCACGAU-3’

Answer: (2) 5’-GAUGGCACGAU-3’

Concept Reinforcement: Transcription in Plants

• Coding strand = same as mRNA (but with T instead of U)

• Template strand = opposite and complementary, used by RNA polymerase

• mRNA is always synthesized in 5’ → 3’ direction

CSIR NET Key Takeaways:

• Always check which strand is being used (template vs coding)

• Complementary base pairing:

  • A → U

  • T → A

  • G → C

  • C → G

• Directionality matters – read the template 3’ → 5’, synthesize RNA 5’ → 3’

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