You are investigating a mutant eukaryotic cell line that makes all of its mrnas much longer than the mrnas from normal cells. intrigued, you examine the proteins in these cells and note that many of them are either much longer or much shorter than the normal proteins from nonmutant cells. assuming there is just one mutant defect in these cells, which of the possibilities is most likely?

a stop codon is mutated
the enzyme that adds the poly-a tail is defective.
rna polymerase does not recognize the terminator sequence.
the spliceosome is nonfunctional.
the release factor is defective.