Final answer:
DNA's structure is a double helix with antiparallel strands forming a backbone of phosphate and sugar groups with pairs of nitrogenous bases as the 'steps'. The bases pair specifically: adenine with thymine, and guanine with cytosine.
Step-by-step explanation:
The correct structure of DNA components can be described using the Watson and Crick model of the double-helix as it was discovered in 1953 at Cambridge University. DNA is composed of two antiparallel nucleic acid chains that form a double helix, resembling a spiral staircase. In this structure, the outside edges are represented by the phosphate and sugar groups (deoxyribose), forming the 'backbone' of the nucleic acid polymer, while the inside 'steps' are the nitrogenous bases pairing in a specific way: adenine (A) always pairs with thymine (T) via two hydrogen bonds, and guanine (G) pairs with cytosine (C) via three hydrogen bonds.
The double-helical structure of DNA is critical because it stores genetic information within the sequence of the four bases along the nucleotide chains. Each nucleotide consists of a phosphate group, deoxyribose sugar, and a nitrogenous base. This structure allows for the accurate replication and transmission of genetic information during cell division, making DNA the primary source of heritable information.