The regular pattern of pairing matches adenine with thymine and cytosine with guanine. The two strands of a DNA molecule are complementary . This means that the nucleotide sequence of one strand will determine the sequence on the opposite strand. This is the key to the molecule's capacity for self-replication. The two strands are also described as anti-parallel .
Information is encoded in the sequence of nucleotides on the DNA molecule.
Different molecules of DNA may be of varying lengths and will have various nucleotide sequences. The complete DNA molecule has the form of a double helix . The two strands twist around each other, giving the molecule a 'spiral staircase' form. The DNA molecule is well-suited to its role as an information blueprint. Many code sequences can be formed from combinations of nucleotides.