The two strands of `DNA` are not identical, but are complementary'. Explain this statement.

Explanation

The two strands in `DNA` molecule are held together by hydrogen bonds between the purine base of one strand and the pyrimidine base of the other and vice versa. Due to the different sizes and geometries of the bases, the only possible pairings in `DNA` are between `G` (guanine) and `C` (cytosine), through three `H-`bonds, i.e., `(C-=G)` and between `A` (adenine) and `T` (thiamine) through two base-pairing principle, the sequnece of base in one strand automatically fixes the sequence of bases in the other strand. thus, the two strands are complimentary and not identified.