RecG has no effect on gene cluster instability in cells with normal BLM. Southern blotting detection of the rDNA clusters in BLM+ cells stably expressing higher levels of co-translated RecG/EGFP, “BLM+: RecG 2a”. Cluster lengths resolved up to 1 Mb are shown. Cluster lengths are calibrated by S. cerevisiae chromosome size markers. Open star is the 1 Mb resolution limit of the gel: all clusters larger than 1 Mb co-localize in this region. A clonal cell population is shown in the far left lane of the gel. A collection of subclonal populations each derived from a single cell of this clonal population are shown to the right. Plum circles: relocated major band clusters. Blue braces: former location of major band clusters from the parental clone.