RNA (ribonucleic acid) is one of the two major nucleic acids in biological cells, the other being DNA; unlike DNA, RNA is single-stranded. The composition of the nucleotides and nucleosides is also partly different due to variations in the monosaccharide and base constituents: D-ribose sugar replaces 2-deoxy-D-ribose; and the base uracil replaces thymine 1. RNA is usually subdivided into mRNA, rRNA and tRNA forms.
Messenger RNA (mRNA)
In the chromosomes, the genetic code contained in the DNA is transcribed to messenger RNA (mRNA) which passes from the nucleus to the ribosomes, the cytoplasmic organelles responsible for protein synthesis. There are as many mRNA molecules as there are proteins synthesized by the cell; its role is in fact, to act as a matrix on which "to mold" the polypeptide 1.
Ribosomal RNA (rRNA)
Ribosomal RNA is the main component of ribosomes. It represents almost all of the ribonucleic acids: about 80% 2.
Transfer RNA (tRNA)
Transfer RNA is responsible for transporting amino acids to ribosomes 2.