The recommendation is based on similarities amongst eukaryotes and viruses these as linear DNA strands, mRNA capping, and limited binding to proteins (analogizing histones to viral envelopes). RNA splicing, carried out by a sophisticated known as the spliceosome, is the system by which introns, or regions of DNA that do not code for protein, are taken out from the pre-mRNA and the remaining exons related to re-sort a single continuous molecule.