The basic primary transcript modification process is similar for tRNA and rRNA in both eukaryotic and prokaryotic cells. On the other hand, primary transcript processing varies in mRNAs of prokaryotic and eukaryotic cells.<ref name="Cooper GM"/><ref>{{cite journal | vauthors = Varassas SP, Kouvelis VN | title = Mitochondrial Transcription of Entomopathogenic Fungi Reveals Evolutionary Aspects of Mitogenomes | journal = Frontiers in Microbiology| volume = 13 | issue = 821638 | date = 21 March 2022 | pmid = 35387072 | pmc = 8979003 | doi = 10.3389/fmicb.2022.821638 }}</ref> For example, some prokaryotic bacterial mRNAs serve as templates for synthesis of proteins at the same time they are being produced via transcription. Alternatively, pre-mRNA of eukaryotic cells undergo a wide range of modifications prior to their transport from the nucleus to cytoplasm where their mature forms are translated.<ref name="Cooper GM"/> These modifications are responsible for the different types of encoded messages that lead to translation of various types of products. Furthermore, primary transcript processing provides a control for gene expression as well as a regulatory mechanism for the degradation rates of mRNAs. The processing of pre-mRNA in eukaryotic cells includes [[5' cap]]ping, [[polyadenylation|3' polyadenylation]], and [[alternative splicing]].
