The basic principle of using polymerase chain reaction (PCR) for genotyping identification is to utilize the sequence differences between the genes of genetically engineered rats and mice and the corresponding wild-type genes. By amplifying the corresponding sequences with PCR and using the band differences in agarose gel electrophoresis (sometimes combined with first-generation sequencing) to distinguish different genotypes. For example, to determine whether an animal is homozygous, heterozygous, or wild-type.