Southern Blot detection of RFLPs

    The Southern Blot autoradiogram (left) shows that a DNA fragment with a sequence homologous to the probe DNA made from clone #10 is present in clones ## 3, 4, & 8, with the expected size of 400bp, and absent in clones ##1 ,2, 5, & 9. [In the control experiment, the probe sticks to itself in lane 10]. In lane #6, a homologous sequence is present, but as two bands, of sizes 300bp and 100bp. This indicates that the homologous DNA is present, but has an additional restriction site that cuts the fragment into two smaller fragments, 100bp from one end.  Thus, clone #6 shows a restriction fragment length polymorphism (RFLP), indicative of DNA sequence variation among the clones. The right-hand panel show the autoradiogram in schematic form.
 
Figure modified from © 2000 by Griffiths et al.; schematic figure & text material © 2024 by Steven M. Carr