Reverse image of ethidium bromide-stained agarose gel electrophoretograph and a densitometer trace of each lane. λ DNA was sheared in duplicate at two different flow rates for 20 iterations. Sheared DNA (0.5 μg) was loaded in each sample lane, and 5 μg of a kilobase molecular mass marker was loaded in the outside lanes and separated by gel electrophoresis. The gel photographic image was scanned on a Hewlett-Packard ScanJet IIcx scanner and imported into NIH Image 1.60ppc. The lanes were marked, and an annotated densitometer trace was created with a modified version of the “Gel Plotting” macro. The densitometer traces were not corrected for DNA size/intensity effects. The annotated trace marked the region that represented 90% of the area under the curve (shaded regions). The numbers outside of each shaded region are the bounds of the region in kb. The numbers at left of each densitometer trace (2.1×, 2.0×, etc.) represent the ratio of the upper limit over the lower limit of the size range indicated.