The double helix (DNA structure)

The double helix is the iconic shape of DNA, resembling a twisted ladder. It consists of two long strands made up of nucleotides, which are the building blocks of DNA. Each nucleotide contains a sugar, a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine). The strands run in opposite directions and are held together by pairs of bases that connect via hydrogen bonds—adenine pairs with thymine, and cytosine pairs with guanine. This structure allows DNA to store genetic information and replicate accurately during cell division.