After cells take up one form of this molecule, it becomes accessible for antibody labeling after its target is hydrolyzed with HCl (“h-c-l”) and borax. That form of this molecule is often co-stained with Ki67 (“k-i-67”). This non-methylated molecule is the larger product (-5[1])of a reaction catalyzed by APOBECs, which underpins (-5[1])the first step of bisulfite sequencing. Ethynyl- and bromo·de·oxy (15[1])derivatives of this molecule are used to detect cell proliferation. The letter (*) psi denotes a form of this molecule that may help strengthen binding to the 30S subunit in one structure’s stem-loops. This molecule is generated by de·aminating cytosine, and methylating this molecule’s (10[2])5’ (“five-prime”) carbon yields its more mutation-resistant analog that similarly forms two hydrogen bonds with adenine. For 10 points, what base replaces thymine in RNA? ■END■ (10[2])