A panicked day leads Karen Hopkin to wonder if her sperm donor really is the father of her child.

Karen Hopkin is a freelance writer and the creator of the Studmuffins of Science calendar. Karen received a PhD in biochemistry in 1992, and then traded in her test tubes for a keyboard. A former producer for NPR's Science Friday, Karen currently voices stories for Scientific American's daily podcast, 60-Second Science. She is a coauthor of the textbook Essential Cell Biology and has written for many magazines including Science, New Scientist, The Scientist, and Golf Digest. Karen once led 1200 people in a musical tribute to the inventor of Karaoke, and in her spare time, she collects the signatures of Nobel Laureates on a 1950s-style autograph dog and is a mom to 8-year-old Christopher.