Southern blots of EcoRI digestions of C. tropicalis ATCC 750 DNA (lanes 1 and 7), pMTL21-E4 (lane 3), pCT2 (lane 4), pCT3 (lane 5), pCT4 (lane 2), and λEMBL3 phage DNA containing the second allele of SAPT1 (lane 6) were hybridized to the SAPT1 gene used as a probe. The molecular size markers (kilobases) are indicated to the left.