Fig. 3.

N-ethyl-N-nitrosourea (ENU) mutagenesis. ENU is a chemical mutagen that induces point mutations via transfer of its ethyl group (CH₃) to guanine residues, which in turn causes mispairing during DNA replication. ENU is injected into male mice where it causes mispairing during spermatogenesis, and therefore induces mutations into sperm DNA. Mutagenised mice are mated with female mice of the same strain to generate offspring that have inherited the introduced mutations. Genetic and phenotypic screens are performed to characterise the mutation. m-mutated allele; +–wild type allele.