the nitrogenous bases in the two strands of a DNA double helix are paired through hydrogen bonds (H-bonds) forming specific base pairs . The hallmark of this structure is that Adenine (A) pairs with Thymine (T) via two hydrogen bonds, while Guanine (G) pairs with Cytosine (C) via three hydrogen bonds . This base-pairing rule makes the two strands complementary to each other . Understanding these fundamental molecular interactions is a high-priority strategy for medical aspirants, as NCERT textbooks provide the foundation for approximately 95% of NEET Biology questions .