Molecular Evolution Activities



Online Document

J. L. Hubby and R. C. Lewontin, "A Molecular Approach to the Study of Genic Heterozygosity in Natural Populations. I. The Number of Alleles at Different Loci in Drosophila pseudoobscura," Genetics 54 (1966): 546-595.
[Summary] [PDF 3MB]

In this set of two papers, Hubby and Lewontin use protein electrophoresis to determine how much genetic variation there is in Drosophila pseudoobscura. They place this study firmly within the context of traditional evolutionary theory, especially the idea that natural selection acts upon pre-existing genetic and phenotypic differences in nature. The purpose of the first paper (Hubby and Lewontin) is to describe the method they use to elucidate isoallelic variation among numerous individuals at a single locus. Their method relies on the supposition that nucleotide substitutions at the level of the gene will lead to amino acid substitutions in the polypeptide, which will, in most cases, lead to a change in the net charge of the polypeptide. By comparing differences in the electrophoretic mobility of a given protein in many individuals, Lewontin and Hubby believe that they can reach certain conclusions about variation at the genetic level. The fact that all of the electrophoretic differences they found tended to segregate in a Mendelian fashion lends credence to their methodology. In this paper, they report the results of their preliminary investigations, in which they determined that of 21 proteins sampled in various D. psuedoobscura strains, nine appear to show a significant amount of electrophoretic-and therefore genetic-variation. They conclude with a brief discussion of the biases and limitations of their methodology, which they explore more fully in the accompanying paper (see below). (jda)


This page was written by Michael Dietrich and Jay Aronson. It was last updated on May 15, 2004.