Final answer:
Each DNA strand consists of a sequence of nitrogenous bases that form a double helix structure with a sugar-phosphate backbone; this sequence carries genetic information.
Step-by-step explanation:
Each DNA strand is composed of the linear sequence of bases along one side of the molecule. The two DNA strands link together in an antiparallel direction and are twisted to form a double helix. These strands are made up of a sugar-phosphate backbone where the sugar of one nucleotide is bonded to the phosphate group of the next through dehydration synthesis. Projecting from this backbone are the nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G); adenine always pairs with thymine and cytosine with guanine through hydrogen bonds. During DNA replication, each strand serves as a template for the creation of a complementary strand with the help of the enzyme DNA polymerase.
The sequence of these nitrogenous bases along the DNA strand carries the genetic information essential for the production of proteins, which is the central dogma of molecular biology. These base sequences are what form genes, the units of heredity that dictate various biological functions and characteristics.