Final answer:
Option (A), The 5' terminal residue of tRNA is not typically phosphorylated; tRNA maturation involves methylation and addition of a 3' C-C-A terminal sequence with adenosine.
Step-by-step explanation:
The 5' end of a tRNA is not typically phosphorylated in mature tRNA. Instead, the modification at the 5' end of the tRNA molecules involves the addition of a specific nucleotide. However, regarding the 5' terminal residue, the 3' terminal residue is more commonly discussed in the context of tRNA maturation, where the tRNA is finally processed to mature tRNA by methylation, deamination or reduction of some of its bases. The 3' terminal trinucleotide C-C-A (3') sequence is added by tRNA nucleotidyl transferase, and this 3' end of tRNA always has adenosine (A) followed by two cytosines (C).
It is also relevant to note that mRNA processing in eukaryotes involves adding a 5' cap and a 3' poly-A tail. The 5' cap is a 7-methylguanosine cap added to the 5' end of the growing pre-mRNA transcript which aids in protecting the mRNA and is involved in translation initiation. Meanwhile, the 3' end of pre-mRNA receives a poly-A tail that is added after transcription and provides additional protection from degradation.