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. With this in mind, my later work focused on analysis of genetic variation at the DNA level. My initial efforts centered on the ribosomal protein genes from Ranunculus. I used cross hybridization to the maize genes and Southern analysis to isolate the restriction fragment containing the genes from the buttercup, prepared detailed restriction maps, and began preparing a genomic library. It is my ultimate goal, should I return to this work, to compare sequences among a series of alpine Ranunculus species which have diverged from one another at different times, in order to examine the influence of time and of ecological factors upon the rate of genetic divergence.