It is possible to achieve great resolving power in this fashion, discriminating between variants that differ only subtly in shape. In general, in butterflies, Drosophila, or mice, the higher resolution technique has revealed two to three times the amount of enzyme polymorphism previously reported. I have increased the resolution of the technique another notch by employing controlled perturbations of the proteins being compared. The levels of heritable variation detected by high-resolution electrophoretic techniques are unexpectedly high, so I set out to test the underlying genetic assumption that the genetic variants of an enzyme are alleles of the same locus. As all lines have identical XDH genes, no genetic variation in XDH enzyme should be observed unless produced by other genes on chromosome 2.
Considerable variation is detected.
Apparently the high resolution gels are detecting not only allelic variation but also subtle transcriptional modifications. It seems clear from the results of these years that analyzing enzyme variation in nature may not be the straightforward problem it first appeared. Progress will require detailed genetic analysis. Few organisms offer the genetic power of meiotic analysis in Drosophila, however. The alpine butterflies, for example, have 62 chromosomes, and can be raised in the lab only with difficulty.