Fig. 1.

Sequences of alleles of the MDR1 promoter region in several strains show polymorphisms. Panel a Strain names are given at left. For heterozygotes, the two alleles are denoted 1 and 2. The position of the residue relative to the start of the MDR1 open reading frame using the sequence from SC5314 is shown above. The sequence at each position in the allele indicated is shown. The nucleotides at these five positions were used to define two alleles of this MDR1 promoter region, termed the A allele and the G allele. Panel b Twenty micrograms of genomic DNA extracted from the indicated strains was digested with AseI and probed in a Southern blot. The mobilities of the bands produced from the G allele and A allele are indicated at right. The letters shown below indicate the alleles present in each strain