Ribonucleic acid (RNA) occurs primarily as single strands, often giving rise to single polynucleotide structures. RNA is a polymeric molecule that is responsible for the regulation, coding, decoding and expression of genes. Each nucleotide has a ribose sugar attached to the carbon, a base that is composed of purines and pyrimidines, a negatively charge phosphate groups and a hydroxyl group which causes helix to mostly adopt the A-form geometry.