one of the salient features of the DNA double-helix is that the two polynucleotide chains have anti-parallel polarity . This means that if one chain runs in the 5'→3' direction, the other runs in the 3'→5' direction . Chemically, the 5' end is defined by a free phosphate moiety, while the 3' end possesses a free hydroxyl (–OH) group . Therefore, being antiparallel implies that the phosphate groups at the start of the two strands are located at opposite ends of the molecule rather than the same end. Understanding this structural orientation is a high-priority strategy, as NCERT textbooks serve as the primary resource for approximately 95% of NEET Biology questions .