The sides of a DNA molecule are made of a repeating sugar-phosphate backbone.

Quick Scoop

Think of DNA like a twisted ladder in your cells.
In that ladder:

  • The “sides” (the rails of the ladder) are made of alternating sugar and phosphate groups, called the sugar-phosphate backbone.
  • The specific sugar in DNA is deoxyribose, a five-carbon sugar that repeats along each strand.
  • These sugars are linked to each other through phosphate groups, forming strong covalent bonds that give DNA its structural stability.
  • The “rungs” of the ladder, by contrast, are the nitrogenous base pairs (A-T and C-G) that connect the two sugar-phosphate sides.

So, when someone asks “what makes up the sides of a DNA molecule,” the answer is:
Alternating deoxyribose sugars and phosphate groups forming the sugar- phosphate backbone.

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