Final answer:
The two sides of a DNA "ladder" are made up of alternating sugar and phosphate groups forming the molecule's backbone, connected by pairs of complementary nitrogenous bases—adenine with thymine, and cytosine with guanine—that form the ladder's rungs.
Step-by-step explanation:
The two sides of a DNA "ladder" are composed of alternating sugar and phosphate groups, which together form the backbone of the DNA structure. These backbones are attached to each other by pairs of nitrogenous bases that form the rungs of the ladder: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).
Because of their shapes and charges, these base pairs bond predictably—with adenine always binding with thymine, and cytosine with guanine—via hydrogen bonds. This complementary base pairing is crucial for DNA replication and transcription as it ensures that the genetic information can be copied accurately.The DNA molecule features two strands that are antiparallel, meaning they run in opposite directions. This antiparallel arrangement facilitates the enzymes that duplicate DNA and read its code to synthesize proteins. The double-helix structure is stabilized by the hydrogen bonds between the bases of the complementary strands.