How is DNA structured?

DNA is structured as a double helix composed of nucleotides, which is a fundamental feature that distinguishes it from other types of biological molecules. The double helix resembles a twisted ladder, where the sides of the ladder are formed by sugar and phosphate molecules, while the rungs are made up of pairs of nitrogenous bases (adenine pairs with thymine, and guanine pairs with cytosine). This configuration is crucial for DNA's function in storing and transmitting genetic information.

The double helix structure allows for the efficient packaging of DNA within cells and provides a mechanism for replication, as the two strands can separate and serve as templates for the creation of new complementary strands. This property is essential for cell division and the reproduction of genetic material.

In contrast, a single strand of nucleotides would not provide the stability and functionality that the double helix does. A circular formation is characteristic of bacterial DNA but does not represent the general structure of DNA found in most organisms, such as humans. Lastly, DNA is not structured as sheets of protein; instead, proteins may interact with DNA, but they are distinct biological molecules with different roles. Overall, the double helix structure is integral to the unique properties and functionality of DNA in living organisms.