Next, we crafted a query using the MouseMine portal53 (http://www.mousemine.org) to access the MGI database, using MP:0002089 as the search criteria in the “Mammalian phenotypes --> Mouse genotypes” template (http://www.mousemine.org/mousemine/template.do?name=MPhenotype_MFeature&scope=all). We asked for all targeted alleles on chromosomes 1–19, X and Y, reasoning that many non-targeted (i.e. random, chemical and radiation-induced) mutations have not been precisely mapped, making it difficult if not impossible to ensure that they are not counted multiple times. Also, in the context of our study, we are discussing the chance that a targeted knockout would give a specific phenotype, so these types of alleles are most relevant. Finally, we excluded alleles present only as cell lines, resulting in 2166 unique genes.
