Final answer:
Exons are the sequences in an mRNA molecule that remain after splicing and code for a polypeptide.
Step-by-step explanation:
The sequences in an mRNA molecule that remain after splicing and code for a polypeptide are called exons.
Splicing is the process by which non-coding regions called introns are removed from the pre-mRNA transcript, leaving behind the protein-coding exons. These exons are then pasted together to form the final mRNA molecule that will be translated into a polypeptide.