Why is the structure of a dna molecule sometimes referred to as having the the shape of a spiral staircase

dna molecules have have nitrogenous base pairs that compliment with each other. ex: guanine, adenine, thymine and cytosine. A:T, G:C. since each has a pair, they form a ladder as the dna molecule develops. this is why it's similar to the shape of a spiral staircase. hope i helped ^__^

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