Mark Ptashne (born June 5, 1940 in Chicago) is a molecular biologist and violinist. He currently holds the Ludwig Chair of Molecular Biology at Memorial Sloan–Kettering Cancer Center in New York. He was the first scientist to demonstrate specific binding between protein and DNA, and his lifelong work has been the elucidation of the molecular mechanisms of switch between lytic and lysogenic lifecyle of bacteriophage lambda, as well as how the yeast transcriptional activator Gal4 works. He was the originator of the "ball and stick" model of transcription factor function, demonstrating in bacteria and in yeast that they typically consist of separable regions that mediate DNA binding and interaction with transcriptional activators or repressors. In 1980 he cofounded Genetics Institute, Inc. with Thomas Maniatis, which was acquired by Wyeth 1996. In 1985, he was awarded the Louisa Gross Horwitz Prize from Columbia University. He won the Albert Lasker Award for Basic Medical Research in 1997, and the Massry Prize from the Keck School of Medicine, University of Southern California in 1998. He has written popular books for a wider scientific audience, including his book Genes and Signals.