Genetically Contaminated BALB/c Nude Mice

Summary

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.

Isoenzyme tests performed on a sample of the animals obtained in 1983 showed that most of the animals were heterozygous for one or more loci. Another series of tests in early 1984, performed on newly acquired mice of the same commerial breeder, confirmed the earlier results. There is no doubt that the animals, which were sold as BALB/cABom nude mice, did not meet internationally accepted standards of a “congenic” line. The use of the strain code “BALB/c” for this population of mice is absolutely inacceptable.