Over past decade it has been noticed that structural and functional homologies extend across very distantly related species. Now day’s homology to a relevant orthologus gene is a criterion of extracting the candidency of a gene to a disease. Virtually every mouse gene has the exact counterparts as human, and the same probably do for other mammalian species.
Mouse chromosome 7 has p locus which is a site of mutation affects pigmentation and often associated with neurologic abnormalities suggests that PWS may result from an imprinting effect on the human homologous of mouse p locus (Nakatsu et al., 1992). In 1998 Yang et al. created two mutations in mice to understand PWS symptoms, the mutated part mapped the sequences of first exon of SNRPN gene and manifested several phenotypes, which was quite common to the PWS. Paternally inherited mice with imprinting center deletion died as neonates and 72% within 48 hours. Neonates detected with a little hypotonia and underweight. In another experiment done in 1999 reported the characterization after the insertion of a transgene in to mouse chromosome 7C, which resulted to PWS and Angelman Syndrome symptoms. By FISH and epigenotype it has been determined that mouse had a complete deletion of the homologous gene to PWS, except flanking loci. It was noticed that the mouse maintained to correctly imprint the male and female germ cells (Gabriel et al., 1999). These approaches in the animal models could be useful for the identification of etiology of gene and mechanisms, phenotypic basis and therapeutics.