Question

The addition of poly(A) tails to 3' end is a characteristic feature of:

• A. Translation
• B. Transcription
• C. Post-translational modification
• D. Post-transcriptional modification

Hint:

Remember the central dogma flow: DNA $\rightarrow$ Transcription $\rightarrow$ pre-mRNA $\rightarrow$ Post-transcriptional modification $\rightarrow$ mRNA $\rightarrow$ Translation $\rightarrow$ Protein $\rightarrow$ Post-translational modification. Placing polyadenylation in this sequence helps identify it correctly.

Answer 1

The Correct Option is D

Step 1: Concept Overview:
Eukaryotic gene expression proceeds through several stages. Initially, a gene's DNA sequence is transcribed into pre-mRNA. Subsequently, this pre-mRNA undergoes modifications, resulting in mature mRNA ready for translation into protein. These modifications are collectively termed post-transcriptional modifications.
Step 2: Detailed Breakdown:
- Transcription: The synthesis of an RNA copy from a DNA template, yielding pre-mRNA.
- Post-transcriptional Modification: The conversion of pre-mRNA to mature mRNA, encompassing:
1. 5' Capping: Addition of a modified guanine nucleotide to the 5' end.
2. Splicing: Removal of non-coding introns and joining of coding exons.
3. Polyadenylation: Attachment of a poly-A tail to the 3' end, essential for mRNA stability, export, and translation.
- Translation: The decoding of mRNA's genetic code into a specific amino acid sequence, forming a polypeptide chain. This occurs after post-transcriptional events.
- Post-translational Modification: Chemical alterations to a protein following its synthesis during translation.
Step 3: Conclusion:
The poly(A) tail addition at the 3' end of the RNA transcript is a key post-transcriptional event, occurring after transcription but before translation.