Which molecules form the 'rungs' of the DNA ladder?

The 'rungs' of the DNA ladder are formed by bases. DNA, or deoxyribonucleic acid, is structured as a double helix, resembling a twisted ladder. The sides of this ladder are made up of alternating sugar and phosphate groups, while the rungs, which connect the two strands of the helix, are composed of nitrogenous bases. These bases include adenine, thymine, cytosine, and guanine. The specific pairing of these bases—adenine with thymine and cytosine with guanine—provides the genetic instructions necessary for cellular function and inheritance. Thus, stating that bases form the rungs emphasizes their crucial role in maintaining the structure of DNA and facilitating its function in encoding genetic information. Other options like phosphates and sugars are important components of the DNA structure but do not contribute to the configuration of the rungs themselves.