Chapter 1 - RNA and the Cellular Biochemistry Revisited

Abstract

This chapter focuses on the study of ribonucleic acid (RNA) and its transcription. RNA is a long, unbranched polymer of ribonucleoside monophosphate moieties joined together by phosphodiester linkages, and both eukaryotic and prokaryotic RNAs are essentially single-stranded molecules. RNA molecules are produced by the process of transcription; wherein, transcription is the process by which a single-stranded RNA molecule is synthesized from a specific chromosome locus. The RNA molecule that results from the transcription of an operon is usually polycistronic, meaning that more than one polypeptide is encoded in a single RNA transcript and the immediate products of transcription are RNA molecules whose sequence correlates precisely with the DNA from which it is derived. These primary transcription products are only a precursor to functional RNA. The synthesis of RNA is mediated by the activity of enzymes known as RNA polymerases. Transcription results in the production of transcripts. These transcripts observed within a cell are broadly classified as ribosomal RNA (rRNA), transfer RNA (tRNA), heterogeneous nuclear RNA (hnRNA), or messenger RNA (mRNA). The rRNA is the most abundant RNA component in the cell whereas the tRNA is responsible for the transportation of amino acids to the ribosome to support de novo protein synthesis. The mRNA drives the phenotype of the cell, although it is the least abundant of all transcript types.