Biology – Structure of nucleic acids and replication of DNA | e-Consult

In eukaryotes, mRNA undergoes several processing steps after transcription to become mature mRNA, which is ready for translation. These modifications are essential for mRNA stability, transport, and accurate translation.

Capping: A 5' cap, consisting of a modified guanine nucleotide, is added to the 5' end of the pre-mRNA molecule. This cap protects the mRNA from degradation by cellular enzymes and is also recognized by the ribosome during translation, ensuring the mRNA is correctly bound and translated.

Splicing: Eukaryotic genes contain non-coding regions called introns, which are removed by a process called splicing. Splicing is carried out by a complex called the spliceosome. This process joins together the coding regions (exons) of the pre-mRNA, creating a continuous coding sequence. Alternative splicing allows for different protein isoforms to be produced from a single gene.

Polyadenylation: A poly(A) tail, consisting of a string of adenine nucleotides, is added to the 3' end of the pre-mRNA molecule. This tail also protects the mRNA from degradation and enhances its export from the nucleus. The poly(A) tail also plays a role in translation initiation.

These modifications are crucial for ensuring that the mRNA is stable, correctly transported to the cytoplasm, and accurately translated into a protein. Without these modifications, the mRNA would be vulnerable to degradation, might not be correctly read by the ribosome, and could lead to the production of non-functional or incorrect proteins.