Lorraine Symington, professor of microbiology and immunology at Columbia University, will present two talks at the Medical Center Thursday, March 20. At 2 p.m., she’ll present “Mechanism and Regulation of DNA Double-Strand Break Repair” at 2 p.m. in Auditorium K-307 (3-6408) for the Department of Biochemistry and Biophysics Seminar Series. At 3 p.m., she’ll discuss “The Joy of Cooking: From Cookies to Plasmids” at the Graduate Women in Science meeting in the Case Method Room (1-9576).