Which part of a DNA molecule creates the genetic code?

The genetic code is determined by the sequence of nitrogen bases in a DNA molecule. DNA consists of four different nitrogen bases: adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair specifically—adenine with thymine and cytosine with guanine—forming the rungs of the DNA ladder. The order of these nitrogen bases encodes the information for building proteins, which ultimately determines the traits of an organism. Each group of three bases, called a codon, corresponds to a specific amino acid in a protein, illustrating how the sequence of nitrogen bases directly influences genetic expression.

In contrast, the sugar and phosphate components of the DNA backbone serve structural roles but do not contain information about the genetic code. Histones, on the other hand, are proteins that help package DNA into a compact form in the nucleus but do not contribute to the genetic code itself. Therefore, it is the nitrogen bases that hold the key to the genetic information within a DNA molecule.