Figure 4.

(A) A Southern blot containing WT (lane 1) and btu2::bsr1 transformant genomic DNA (lane 2) digested with HindIII restriction endonuclease. The blot was probed with an α-[³²P] ATP–labeled fragment containing the 3′-untranslated region of BTU2. In WT, the probe detects a 3.0-kb fragment of the BTU2 gene. Gene disruption of BTU2 using the btu2::bsr1 fragment eliminates one HindIII site (H) and yields a fragment of 4.8 kb (see diagram on the right). The transformant DNA contains the 4.8-kb fragment and the endogenous 3-kb fragment, indicating that the transformant is heterozygous for btu2::bsr1/BTU2. (B) A Southern blot of total genomic DNA of WT (lane 1) and btu1::neo1 transformant (lane 2) probed with a 3′-untranslated fragment of BTU1. In WT, an 8-kb HindIII fragment was detected. In the transformed cell, a smaller 2.3-kb fragment was detected consistent with gene knockout of BTU1, which should introduce an additional HindIII site (H, see diagram on the right).