Question

##If the 3' of ribose (or deoxyribose) is replaced by an H, what happens to the synthesis of RNA# (or DNA)?

Answer 1

Generally, nucleotide =Nucleoside + phosphate group

Nucleoside =Ribose sugar +nitrogenous base

Now Ribose/deoxyribose sugar is a 5 carbon sugar. In Ribose sugar both 2 and 3 no carbon contain Hydroxyl (-OH )group, but in Deoxyribose sugar only 3 no carbon contain Hydroxyl (-OH)group.These 3' OH group play important role in DNA (Deoxyribose)and RNA(Ribose) synthesis. These free 3' -OH group act as a nucleophile and attack to the Alpha phosphate ( this reaction known as nucleophilic substitution reaction or SN2 ) of upcoming nucleotide residue and form 5'-3' Phosphodiester bond,and synthesized DNA/RNA.now if these 3' OH group replaced by H then addition of upcoming nucleotide will be blocked and DNA/RNA synthesis also stopped.