Which description applies to alternative mrna splicing? a-protein modifications such as addition of a functional group, or structural changes such as foldingb-heritable changes in gene expression that occur without altering the dna sequencec-a gene cluster controlled by a single promoter that transcribes to a single mrna strandd-mrna modifications such as additions of a 5'-cap and 3' poly-a tail and removal of intronse-processing of exons in mrna that results in a single gene coding for multiple proteins