FIG. 3.

(A) Monoallelic expression of Sgce in interspecific embryos by RFLP analysis. A PCR fragment was amplified from both C57BL/6J and M. spretus and sequenced. In lanes 1 to 4, the 404-bp fragment is amplified in both species. In lanes 5 to 7, only the C57BL/6J product is cut with RsaI. In embryonic cDNAs from the interspecific cross, the 404-bp fragment is undigested by RsaI, showing exclusive paternal (M. spretus) expression (lane 8), as seen also for adult tissues (lanes 10 to 12). Only in the adult interspecific brain is weak expression of the maternal allele detected (lane 9). Lane 13 is a control showing coamplification of M. musculus and M. spretus alleles after they are mixed in the same reaction. (B) Paternal expression of Zac1 in interspecific embryos by RFLP analysis. A 465-bp PCR fragment was amplified from both C57BL/6J and M. m. castaneus and digested with BstNI. M. m. castaneus produces three fragments, of 311, 124, and 30 bp (lane 1), whereas the C57BL/6 allele produces two fragments, of 311 and 154 bp (lane 4). Embryo and MEF interspecific cDNA from reciprocal crosses revealed that only the paternal allele is expressed (lanes 2, 4, 13, and 14). In adult tissues, biparental expression is most apparent in the liver (lane 9) and to a lesser extent in kidney and skeletal muscle (lanes 7 and 8).