Final answer:
The rungs of the DNA ladder are made up of nitrogenous bases, specifically pairs of adenine with thymine and guanine with cytosine. The sides of the ladder are composed of a sugar-phosphate backbone, which consists of alternating sugar and phosphate groups.
Step-by-step explanation:
DNA is shaped like a twisted ladder. The rungs of the ladder are composed of nitrogenous bases while the sides of the ladder are composed of sugar-phosphate molecules.
The DNA molecule, known for its distinctive double helix shape, consists of two complementary strands that wind around each other. The sugar-phosphate backbone forms the sides of this 'ladder,' with alternating sugar (deoxyribose) and phosphate groups. The rungs are made up of base pairs formed by the bonding of nitrogenous bases: adenine with thymine, and guanine with cytosine — these pairs are held together by hydrogen bonds. The arrangement of these components gives DNA its structural integrity and allows for the storage and transmission of genetic information. These strands run in opposite directions, which is described as antiparallel, ensuring proper base pairing during DNA replication and gene expression.