Representative rod and cone flicker responses of control and mutant puppies. A. Representative rod flicker responses (frequency 5Hz; intensity −1.6 log cdS/m2). First column = normal control, second column = PDE6A mutant puppies. B. Representative cone flicker responses (frequency 33 Hz; intensity 0.39 log cdS/m2). First column = normal control, second column = PDE6A mutant puppies. For both A and B the tracings from top to bottom are from 2, 3, 4, 5, 6 and 7 week old puppies. Arrowheads indicate the timing of the flashes.