This student is cramming for her biology test with only a frosting-covered doughnut for lunch. Specialized cells in her pancreas respond to the increasing amount of sugar in her blood by releasing insulin, a small protein that regulates blood sugar levels. Let's go inside one of these cells to see how this protein is manufactured. The instructions for making insulin are coded by a segment of DNA in the nucleus. In transcription, an enzyme zips along the DNA forming RNA, shown here in red. RNA nucleotides line up with their complementary DNA partners, transcribing the information in DNA into RNA.