Scientists are wrong all the time, sometimes for many decades. This is not surprising, as discovery in science is a process of change. Do scientists change their minds when they get new data, or does the data need to be "special"? In this course, we will trace the processes that caused scientists to change their minds about biological discoveries, beginning with the demonstration that genes are made of DNA, and ending with the controversial role of "junk" DNA in the human genome. By investigating what scientists believed when they were wrong, and then following their arguments for and against the incorrect, and correct explanations, we will both understand better the roles of theory and evidence in scientific discovery, and also develop a process for making sense out of abstract models. In addition to following the process of transition from "wrong" to "right" for settled biological science, we will also examine an unsettled question: "Is 90% of the human genome 'junk'?".