Question

Post transcriptional modification includes

• A. RNA editing
• B. Phosphorylation, Acetylation
• C. 5' capping, 3' poly adenylating and intron removal by splicing
• D. Ubiquitination

Hint:

• Post-transcriptional modifications occur primarily in eukaryotes to convert pre-mRNA into mature mRNA.
• Major modifications:
  • 5' cap (7-methylguanosine)
  • 3' poly(A) tail
  • Splicing (removal of introns, joining of exons)
• RNA editing is another, less universal, type of modification.

Answer 1

The Correct Option is C

Post-transcriptional modifications are changes made to the primary RNA transcript (pre-mRNA in eukaryotes) before it is translated into protein. These modifications are crucial for the stability, transport, and proper translation of mRNA in eukaryotes. Key post-transcriptional modifications in eukaryotes include: 1. 5' Capping: Addition of a modified guanine nucleotide (7-methylguanosine cap) to the 5' end of the pre-mRNA. This protects the mRNA from degradation, aids in its export from the nucleus, and is important for ribosome binding during translation initiation. 2. 3' Polyadenylation (Poly(A) tail addition): Addition of a long string of adenine nucleotides (poly(A) tail) to the 3' end of the pre-mRNA. This increases mRNA stability, aids in its export from the nucleus, and plays a role in translation. 3. Splicing (Intron Removal): Removal of non-coding intervening sequences (introns) and joining of the coding sequences (exons) to form a mature, continuous coding mRNA. Let's analyze the options: (a) RNA editing: This is a type of post-transcriptional modification where the nucleotide sequence of an RNA molecule is altered (e.g., insertion, deletion, or substitution of bases). It is a valid modification, but option (c) lists more common and defining ones. (b) Phosphorylation, Acetylation: These are common post-translational modifications of proteins, not usually post-transcriptional modifications of RNA (though RNA can be modified in other ways, these are primarily protein mods). (c) "5' capping, 3' poly adenylating and intron removal by splicing": This lists the three major and most characteristic post-transcriptional modifications of eukaryotic pre-mRNA. (d) Ubiquitination: This is a post-translational modification of proteins, involving the attachment of ubiquitin, often targeting the protein for degradation. Option (c) provides the most comprehensive and common set of post-transcriptional modifications. \[ \boxed{\text{5' capping, 3' poly adenylating and intron removal by splicing}} \]