Introns are removed from mRNA during a process called splicing. This occurs after the initial transcript of mRNA, known as pre-mRNA, is synthesized from DNA. Pre-mRNA contains both exons, which are the coding sequences, and introns, which do not code for proteins.
During splicing, the introns are cut out, and the exons are joined together to form a continuous coding sequence. This process is critical because it ensures that the final mRNA molecule can be translated into a functional protein. The splicing is facilitated by a complex called the spliceosome, which recognizes specific sequences at the intron-exon boundaries, accurately removing the introns and linking the exons.
In summary, splicing is the essential step that transforms pre-mRNA into mature mRNA by removing introns to ensure proper protein synthesis.