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