What are the side rails of DNA called?

The double helix looks like a twisted ladder—the rungs of the ladder are composed of pairs of nitrogenous bases (base pairs), and the sides of the ladder are made up of alternating sugar molecules and phosphate groups.

There are two sides to the double helix, called the sugar-phosphate backbone, as they are made from alternating phosphate groups and deoxyribose sugars. The “steps” of the double helix are made from the base pairs formed between the nitrogenous bases.

- BRAINLIEST answerer

phosphate and deoxyribose molecules

Explanation:

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layer 3 is younger than layer 6.