The recessive jal and Gata3tm1Gsvmutations fail to complement in doubly heterozygous mice. (a) Typical results of a 3-primer PCR test designed to identify Gata3tm1Gsvcarriers. The 320 bp band and a fainter, high-molecular-weight band (marked with an asterisk) are specific to the mutant allele. The size standard shown (MM) is a 50 base pair ladder. A 10-day-old litter from a cross of Gata3tm1Gsv/Gata3+x jal/jal included pups displaying wild type (b) or mutant (c) hair development. All phenotypically wild type pups showed the 399 bp band only, and the phenotypically mutant pups all carried the targeted mutation. The snouts of one wild type (d) and one mutant (e) pup from the same litter are enlarged to show normal vs. defective vibrissae formation, respectively.