Confirmation of null mutation by Northern analysis of poly(A)⁺ mRNA extracted from kidneys and testes of IL11Ra+/+, IL11Ra+/−, and IL11Ra−/− mice. The blot was initially examined with a probe encoding the deleted region of the IL11Ra locus (A) and then with a probe situated in the locus 5′ of the deleted region (B) and rat GAPDH to compare mRNA loading (C). The size of the transcript is indicated.