mouse strain C57BL/6 mouse strain C57 http://en.wikipedia.org/wiki/C57BL/6 black 6 C57 black 6 Person:Jie Zheng A mouse strain that is a laboratory mouse generated from long inbreeding with nearly identical genotype. C57BL/6 mouse has a dark brown, nearly black coat, and an easily irritable temperament. It has a good reproductive performance and is the most widely used "genetic background" for genetically modified mice for use as models of human disease.