Abstract: The invention provides a collection of paired samples from a plurality of mutagenized animals, wherein each paired sample comprises: a first sample comprising genetic screening material of an animal; and a second sample comprising reproductive material of that same animal. A sample of reproductive material according to the invention can be used to generate a progeny animal carrying that same mutation. The invention also provides a collection of pairs of mutant genomes, comprising a plurality of animals carrying induced mutations and a corresponding plurality of sample genomic material, wherein a pair of mutated genomes of the collection comprises an animal having a genome containing an induced mutation and the animal's sample genomic material. The mutant animal, which might need to be bred to homozygosity, is useful for investigating the function of the gene. It might also be a useful animal model for studying human disease.