Ribonucleic acid polymerase specificity

Chamberlin, M., Ring, J. Characterization of T7-specific ribonucleic acid polymerase. 

In like manner, ribosomal ribonucleic acid (rRNA) and transfer ribonucleic acid (tRNA) are synthesized from their specific genes through the action of DNA-dependent RNA polymerase. And as in the case of mRNA, each of the precursor forms of these nucleotides are also processed until they reach their final forms. The rRNAs and a large variety of ribosomal proteins are assembled to form the ribosome. Ribosomes, the supramolecular structures in which protein synthesis takes place and which functionally resemble multienzyme complexes, are elaborate structures. They are attached, by a binding site on the smaller subribosomal particle, to the endoplasmic reticulum. The tRNAs that are synthesized finally become charged with specific amino acids. 

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