Genetically Contaminated BALB/c Nude Mice

BALB/cABom nude mice, in the course of 1983 and early 1984 obtained from a commercial breeding company, were found to differ significantly from the standard genotype of BALB/c mice. The first indications for genetic contamination came from behaviour and reproductive performance of the bought population of animals; they did not resemble inbred BALB/c’s, their gestation period was too short and their litter size unusually high.