This tutorial introduces chemical compounds
Types of RNA
mRNA represents about 5-10% of cellular RNA. It contains the sequence of bases coding for a particular amino acid sequence in a polypeptide chain. tRNA represents about 15-20% of cellular RNA. Each tRNA molecule is specific for one amino acid. There is an enzyme for each amino acid which recognizes the amino acid and its specific tRNA and joins the two together. The specific joining of tRNA to amino acid is the only place where the genetic code is realized. rRNA represents about 70-80% of cellular RNA. It is associated with specific set of ribosomal proteins. It functions as non-specific ‘workbench’ for the assembly of polypeptides. Many copies of genes coding for rRNA are located in nucleolar organizer regions of certain chromosomes.
Protein Synthesis -Translation and Regulation
Ribonucleic acids are made up of nitrogenous bases such as adenine, Uracil, guanine and cytosine, ribose sugar and phosphate group. RNA is normally single stranded which can have a diverse form of secondary structures other than duplex. tRNA shows secondary and tertiary structure. RNA synthesis is the process of transcribing DNA nucleotide sequence information into RNA sequence information. RNA synthesis is catalyzed by a large enzyme called RNA polymerase. RNA synthesis involves three steps: Initiation, elongation and termination. RNA splicing is a process that removes introns and joins exons in a primary transcript. Post transcriptional changes take place and mRNA, tRNA and rRNA are processed.
RNA synthesis occurs in both prokaryotes and eukaryotes. There are three steps to RNA synthesis: Initiation, elongation and termination. In the initiation step, RNA polymerase binds to gene regulatory elements. In the elongation step, RNA polymerase unwinds DNA duplex next to a gene. RNA is transcribed 5’ to 3’ from the template of 3’ to 5’. Termination in eukaryotes is by cleavage and polyadenylation.