The shape of DNA is called a double helix or duplex structure. This structure consists of two strands that run in two opposite directions, such as the 5 to 3 direction and the 3 to 5 direction. The two strands are connected by chemical bonds between the bases: adenine bonds with thymine, and cytosine bonds with guanine. The nitrogenous bases pair up to make each step of the ladder, and they only pair up in a specific way. Adenine always pairs with thymine, and guanine always pairs with cytosine. The double helix shape of DNA is important because it allows the molecule to store and transmit genetic information. The shape of DNA was first discovered by James Watson, Francis Crick, and Rosalind Franklin.