Biology – Protein synthesis | e-Consult

Following transcription, the primary RNA transcript (pre-mRNA) undergoes significant processing to become mature mRNA. This processing is crucial for ensuring the production of functional proteins. The primary transcript contains both coding sequences (exons) and non-coding sequences (introns). Introns are segments of RNA that do not code for protein and are interspersed with exons, which contain the protein-coding information.

The key process in RNA processing is splicing. This involves the removal of introns and the joining together of exons. Splicing is carried out by a complex molecular machinery called the spliceosome, which is composed of small nuclear RNAs (snRNAs) and proteins. The spliceosome recognizes specific sequences at the boundaries of introns and exons. These sequences include 5' splice sites, 3' splice sites, and a branch point sequence. The spliceosome then excises the introns and ligates (joins) the exons together.

There are different types of splicing, including constitutive splicing, where all introns are removed, and alternative splicing, where different combinations of exons can be included in the mature mRNA. This allows a single gene to code for multiple different protein isoforms, increasing protein diversity.

The significance of RNA processing is that it produces a mature mRNA molecule that contains only the protein-coding information. This ensures that the ribosome can accurately translate the mRNA into a functional protein. Furthermore, alternative splicing allows for greater protein complexity and regulation.