MUTATION UNITS OF LOCI CODING FOR LACTATE -DEHYDROGENASE AND THEIR DIRECTED CHANGES IN THE PHYLOGENESIS OF VERTEBRATES

Comparison of the electrophoretic mobility of various alleles of Mh-A and B loci within and between species demonstrated a decreased range o f variation from fish to anuran amphibians and from anurans to mammals . Fish and mammals feature incompatible ranges of this variation, usua lly having a mobility range above and below the first zone of Ldh-A an d B loci heterodimers, respectively. Amphibians feature both types of variation. Such a quality difference in allelic variation may result f rom scaling down the amino acid changes from mutation of intragenic re gions in fish to single amino acid substitutions in mammals.