FIG. 3.

Effect of spacer length on efficiency of cleavage and recombination. All substrates carried two recognition sites in tail-to-tail orientation, separated by the number of base pairs given above the lanes. Labels and markers are as in Fig. 2. Two independent experiments are shown, one (A) covering a broad range of recognition site separations and the other (B) focusing on the range from 12 to 20 bp. About 0.3 fmol of DNA and 70 fmol of QQR were injected in each sample. (C) Histogram summarizing the results of several independent oocyte injection experiments. Recombination yields are plotted against the distance in base pairs between inverted sites. Values were normalized to the recombination fraction measured for pQT8 in each experiment; thin lines represent standard deviations from three or four independent experiments. The values for spacers of 14 and 18 bp are based on a single experiment but were confirmed qualitatively by two additional observations.