which one?

Which statement describes an operon? mRNA modifications, such as the addition of a 5'-cap and 3' poly-A tail and the removal of introns a gene cluster controlled by a single promoter that transcribes to a single mRNA strand the processing of exons in mRNA that results in a single gene coding for multiple proteins protein modifications such as the addition of a functional group, or alternate folding of the protein heritable changes in gene expression that occur without altering the DNA sequence