What happens to the introns within a pre-mRNA molecule during processing?

During the processing of a pre-mRNA molecule, introns, which are non-coding sequences, are spliced out. This process is crucial for generating a mature mRNA that contains only the coding sequences, known as exons, which are necessary for translation into proteins. The removal of introns helps ensure that the resulting mRNA accurately reflects the protein-coding information required for gene expression. This splicing event is facilitated by a complex known as the spliceosome, which recognizes specific sequences at the intron-exon boundaries.

In contrast to this, the other options do not accurately describe the fate of introns. Introns are not translated into proteins, nor do they remain unchanged or get added to the 5' cap of the mRNA. The cap is added to the 5' end of the mRNA molecule to protect it from degradation and assist in ribosome binding during translation, while introns are discarded entirely during the splicing process.