Question

Describe the structure of RNA polynucleotide chain having four different types of nucleotides.

Answer 1

A RNA nucleotide has three main components − a nitrogenous base, a ribose sugar and a phosphate group.

• The ribose sugar and the phosphates form the backbone of a polynucleotide chain with nitrogenous bases linked to sugar moiety and projecting from the backbone.

• Two types of nitrogenous bases are present i.e. Purines (Adenine and Guanine) and Pyrimidines (Cytosine and Uracil).

• A nitrogenous base is linked to the ribose sugar through N-glycosidic linkages to form a nucleoside (like adenosine, guanosine or cytidine and uridine).

• A phosphate group is linked to 5'-OH of a nucleoside through phosphoester linkage to form a corresponding nucleotide.

• Every nucleotide residue has an additional −OH group present at 2' -position in the ribose.

• Many nucleotides are linked through 3'-5' phosphodiester linkages to each other to form the polynucleotide chain.

• The end of the chain which has a free phosphate moiety at 5'-end of ribose sugar is referred to as 5’-end and the other end of the chain having a free 3'-OH group at the ribose sugar is referred to as 3' -end of the polynucleotide chain.