Answer:
We identify nucleic acid strand orientation on the basis of important chemical functional groups. These are the phosphate group attached to the 5' carbon atom of the sugar portion of a nucleotide and the hydroxyl group attached to the 3' carbon atom
Step-by-step explanation:
Nucleic acids are polymers formed by a phosphate group, a sugar (ribose in RNA and deoxyribose in DNA) and a nitrogenous base. In the chain, the phosphate groups are linked to the 5'-carbon and 3'-carbon of the ribose (or deoxyribose) and the nitrogenous base is linked to the 2-carbon. Based on this structure, the nucleic acid chain orientation is identified as the 5'-end (the free phosphate group linked to 5'-carbon of the sugar) and the 3'-end (the free hydroxyl group in the sugar in 3' position).