N or J? Black 6 Substrains Have Diverged (IMAGE) Jackson Laboratory Caption Separated by more than six decades, the C57BL/6N substrain (left) of laboratory mouse has undergone multiple genetic changes due to spontaneous mutations and is now visibly different from the founder strain, the C57BL/6J of The Jackson Laboratory. Credit The Jackson Laboratory Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.