Question

A nucleic acid can be synthesized only in the direction of

• A. 5-3
• B. 3-5
• C. 5-5
• D. 3-3

Answer 1

The correct option is A 5-3

A nucleic acid can be synthesized only in the direction of 5-3. The main feature of nucleic acids is that they have two distinctive ends: the 5' (5-prime) and 3' (3-prime) ends. This terminology refers to the 5' and 3' carbons on the sugar. The process involves forming phosphodiester bonds between the 3' carbon of one nucleotide and the 5' carbon of another nucleotide. This leads to formation of the so-called "sugar-phosphate backbone". For both DNA and RNA, the 5' end bears a phosphate, and the 3' end a hydroxyl group.