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R. C. Lewontin and J. L. Hubby, "A Molecular Approach to the Study of Genic Heterozygosity in Natural Populations. II. Amount of Variation and Degree of Heterozygosity in Natural Populations of Drosophila pseudoobscura," Genetics 54 (1966): 595-609.
[Summary] [PDF 1010K]

The purpose of this accompanying paper is to describe the results they achieved when they applied their experimental system (see Hubby and Lewontin 1966, above) to a wild population of Drosophila pseudoobscura. They show that there is a great deal of variation in electrophoretic mobility in many of the proteins they study. Following from this, they conclude that there is genetic variation at 39% of loci in the D. pseudoobscura genome. Even so, the authors have found what they believe to be "striking" amounts of variation in certain proteins they studied. They expressed surprise that even the strains that had been kept in the laboratory for several years showed a tremendous amount of heterozygosity. Further, they are unable to find any instances of "pure local races," in which some populations homozygous for one allele and other populations homozygous for a different one. In the course of their paper, Lewontin and Hubby attempt to calculate the proportion of loci at which an individual in a given population will be heterozygous. They call this "the central problem of experimental population genetics at the present time. " Lewontin and Hubby point out, however, that because of the many limitations of their method-they list four-it is only possible to capture a small amount of the variation that actually exists in natural populations. Lewontin and Hubby explicitly state that they are not willing to choose among hypotheses regarding the "balance of forces" responsible for the high degree of genetic variation they observe, though they state that such variation is in need of an explanation. (jda)


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