In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

method of determining certain modifications of this substance involves treating it with bisulfite, and a type of bonding named for Hoogsteen is sometimes observed in this substance. The binding of proteins to this substance can be studied via footprinting assays, and proteins which bind to this substance usually contain structures such as zinc-finger domains and leucine zippers. Chargaff's observations helped interpret the bonding of its constituent parts. For 10 points, identify this substance composed of thymine, adenine, cytosine, and guanine, which is located in the nucleus and which can be transcribed to give RNA.
Science