This image depicts the chemical structure of cytosine. It shows a hexagonal ring with nitrogen atoms at positions 1 and 3, and a primary amine group attached to carbon 4. The two remaining positions ...

and the ratio of guanine to cytosine, are always very close to unity for deoxyribose nucleic acid. It is probably impossible to build this structure with a ribose sugar in place of the deoxyribose ...

According to this rule, the amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine in a double-stranded DNA molecule. This 1:1 ratio of A:T ...

Beyond the ladder-like structure described above, another key characteristic of double-stranded DNA is its unique three-dimensional shape. The first photographic evidence of this shape was ...