Final answer:
RNA splicing occurs during transcription. About 70 percent of genes in humans are expressed as multiple proteins through alternative splicing.
Step-by-step explanation:
RNA splicing occurs during transcription. It is a process in which the introns, non-coding regions of DNA, are removed from the pre-mRNA molecule before it matures into mRNA. The remaining exon sequences are then spliced together to form the final mRNA that will be translated into protein. About 70 percent of genes in humans are expressed as multiple proteins through alternative splicing.