Abstract
Because of the similarity of their allelic profiles it was assumed that 'ICR' non-inbred mouse colonies were of common origin: however there were differences in allelic frequencies between them. It was also found that the allelic frequency at the C3-1 locus differed between samples from the same colony. Research workers should therefore be aware that the genetic variability of outbred animals may vary among samples, even if the animals are properly designated and supplied from the same breeder.