The rungs of the DNA ladder are made of pairs of nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G) , which pair as A–T and C–G via hydrogen bonds.

Quick Scoop: DNA “ladder” rungs

Think of DNA as a twisted ladder (the famous double helix).

  • The sides of the ladder are sugar–phosphate backbones.
  • The rungs are the paired nitrogenous bases in the middle:
    • Adenine (A) paired with Thymine (T)
    • Cytosine (C) paired with Guanine (G)

These base pairs carry genetic information and are held together by hydrogen bonds, which keep the two strands connected but still allow them to separate during replication and transcription.

So, when someone asks “what are the rungs of the DNA ladder made of ~~”, the clean answer is: they’re made of specific pairs of nitrogenous bases (A–T and C–G).

TL;DR:
Rungs of the DNA ladder = nitrogenous base pairs (A–T and C–G), not sugars or phosphates.

Information gathered from public forums or data available on the internet and portrayed here.