11. tRNA genes of a Gram positive bacteria were sequenced. While some of the genes possessed sequence corresponding to the -CCA end of the tRNA, others did not. Interestingly, even the genes that lacked the sequence corresponding to the -CCA end of the tRNA were found to code for a functional tRNA. This is because
    (1) the -CCA end in the tRNA is not essential for its function.
    (2) the genes that do not possess sequence corresponding to the -CCA ends of the tRNA are repaired prior to their transcription.
    (3) the -CCA end is added to the tRNA during their maturation.
    (4) the primary transcripts of the genes lacking sequence corresponding to the – CCA end are subjected to g-RNA mediated editing prior to their maturation.

Why Do Functional tRNAs Exist Even When Their Genes Lack the -CCA End? (CSIR NET Life Science)

Correct Answer

(3) The -CCA end is added to the tRNA during their maturation.

Detailed Explanation

The -CCA sequence at the 3’ end of tRNA is absolutely essential for its function, as it is the site where amino acids are attached during translation. However, not all tRNA genes encode this -CCA sequence directly. In many bacteria (and all eukaryotes), the -CCA end is added post-transcriptionally by a specialized enzyme called tRNA nucleotidyltransferase during tRNA maturation.

Key Points:

• tRNA Maturation: After a tRNA is transcribed, it undergoes several processing steps, including trimming, base modification, and, crucially, the enzymatic addition of the -CCA sequence at the 3’ end if it is not encoded in the gene.

• Universal Mechanism: This mechanism ensures that all mature tRNAs, regardless of their gene sequence, have the -CCA end necessary for amino acid attachment and participation in translation.

• Functional tRNA: Even if the gene does not contain the -CCA sequence, the mature tRNA will possess it due to this post-transcriptional addition, resulting in a fully functional molecule.

Why Other Options Are Incorrect:

• Option (1): The -CCA end is essential for tRNA function.

• Option (2): There is no repair of tRNA genes prior to transcription; the modification happens after transcription.

• Option (4): g-RNA mediated editing is not involved in tRNA maturation in bacteria.

Why Choose Let’s Talk Academy (LTA) for CSIR NET Life Science?

Let’s Talk Academy (LTA) is the leading platform for CSIR NET Life Science aspirants, offering:

• Free CSIR Previous Year Questions (PYQs): Access a comprehensive collection of topic-wise PYQs at no cost.

• Free Video Solutions: Expert faculty provide detailed explanations and step-by-step solutions in easy-to-understand videos.

• Free Study Material and Test Series: Get high-quality, exam-oriented notes and regular test series to assess and improve your preparation.

LTA’s commitment to accessible, expert-led resources makes it the top choice for Life Science exam preparation.

Summary:
Functional tRNAs are produced even when their genes lack the -CCA end because the -CCA end is added during tRNA maturation (option 3). For more free resources, video solutions, and expert guidance, trust Let’s Talk Academy for your CSIR NET Life Science journey!