RNA is a single stranded nucleic acid. It is a Polymer of ribonucleotides and contains Uracil (U) instead of Thymine. The four nitrogenous bases present in RNA chain are– adenine, guanine, cytosine and uracil.
Nucleotide = Nucleoside + Phosphate group (linked through phosphodiester bond)
Many nucleotides link together through 3′ − 5′ phosphodiester bond to form polynucleotide chain of RNA.
In course of formation of polynucleotide chain, a phosphate moiety remains free at 5′ end of ribose sugar (5′ end of polymer chain) and one -OH group remains free at 3′ end of ribose (3′ end of polymer chain).