Correct option is B
Explanation-
The CCA sequence is added post-transcriptionally by a specialized enzyme called tRNA nucleotidyltransferase. This enzyme does not require a DNA template. Instead, it uses nucleotides (CTP and ATP) to add the C–C–A sequence to the 3′ end of the tRNA. This is why it's said to occur in a template-independent manner.
Incorrect options-
Option a: "In these tRNAs amino acylation occurs at the 3' end in the absence of the CCA sequence."
Aminoacylation (adding amino acid) specifically requires the CCA 3′ end. Without it, aminoacyl-tRNA synthetases cannot attach amino acids.
Option c: "These tRNAs exploit the process of trans-splicing to include a CCA sequence at their 3' end."
Trans-splicing is not used for CCA addition in tRNAs. It’s a different RNA processing mechanism used mostly in some eukaryotic mRNAs.
Option d: "The absence of CCA sequence occurred only in the last common ancestor (LCA) during the course of evolution and the current day tRNA genes always possess a sequence to encode the CCA end of the tRNA."
Even in modern bacteria, many tRNA genes still lack the CCA and rely on enzymatic addition.
So, the correct answer is option b - CCA sequence is added to these tRNA transcripts in a DNA template independent manner.
