RNA consisting of folded molecules that transport amino acids from the cytoplasm of a cell to a ribosome.
- RNA molecules - mainly transfer RNA and ribosomal RNA - also evolve under structural constraints.
- For deep levels of divergence, protein coding genes may be saturated at the amino acid level and highly conserved regions of ribosomal RNA and transfer RNA genes may be useful.
- Of these, a few are transcribed, including clusters of ribosomal RNA, transfer RNA, and histone genes.