After the transcription step is completed, the splicing process begins.
Splicing is the process by which introns from pre-mRNA transcripts are excised and exons link together to generate mature mRNA, which exits the nucleus and participates in protein synthesis.
The function of splicing:
Splicing allows many functional mRNAs to be formed from a single transcript that codes for various proteins.
It also aids in the control of gene expression and cell protein content.
It aids in the evolution process by creating alternative exon combinations and so producing new and better proteins.
To make novel proteins, additional exons can be introduced into introns without interfering with the original gene's activity.