The document summarizes the structure of DNA. It describes that: 1) James Watson and Francis Crick described DNA as a double helix structure. 2) A DNA nucleotide contains a deoxyribose sugar, phosphate group, and a nitrogen base (adenine, cytosine, thymine, or guanine). 3) In DNA, adenine pairs with thymine and guanine pairs with cytosine to form the rungs of the DNA ladder structure.