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Biomedical subjects

T Dobzhansky

Publications and source records attributed to T Dobzhansky.

At least 37 records · Page 2Linked to original sources
PubMed1971

Polymorphisms in continental and island populations of Drosophila willistoni.

A comparative study of genic allozyme and chromosomal polymorphisms in four continental (South American) and six oceanic island (West Indies) populations of Drosophila willistoni has been made. The pattern of genic polymorphism is closely similar in all populations. Although regional and local differences in gene frequencies are found, generally the same alleles occur at high, intermediate, and low frequencies in all populations. An average individual is heterozygous at 18.4 and 16.2% of its loci in the continental and island populations, respectively. By contrast, chromosomal polymorphism is sharply reduced on the islands compared to most continental populations, and some chromosomal inversions are more frequent on some islands than on others. The observations are not compatible with the hypothesis that most of the gene variants are adaptively neutral. Balancing natural selection is responsible for most of the genic polymorphism in natural populations of D. willistoni.

Alleles↗
PubMed1970

Enzyme variability in the Drosophila willistoni group. I. Genetic differentiation among sibling species.

We have studied by gel electrophoresis the variability of 14 structural genes in four sibling species, Drosophila willistoni, D. paulistorum, D. equinoxialis, and D. tropicalis. Samples of about 30 populations from different parts of the distribution areas of each species were examined. Genetic variants are found at every locus; 67% of the loci are polymorphic, having two or more alleles, the rarer of which has a frequency of 5% or higher. The gene frequencies are fairly uniform over the distribution area of each species, but considerably different in different species. It is estimated that individuals which belong to the different species differ on the average in somewhat more than one half of their gene loci. The morphological similarity of the four sibling species contrasts with the extensive diversity in their genetic materials.

Animals↗
PubMed1969

Artificial and natural selection for two behavioral traits in Drosophila pseudoobscura.

In an attempt to elucidate the genetic architecture of two behavioral traits, populations of Drosophila pseudoobscura were selected for positive and for negative phototaxis and geotaxis. The selected populations diverged rapidly in their behavior (Figs. 1 and 2). The selection was relaxed after 20 generations in the phototactic, and after 30 generations in the geotactic populations. The relaxation resulted in convergence almost as rapid as was the divergence under selection. The average phototactic and geotactic neutrality of natural populations is an adaptive trait protected by genetic homeostasis. This does not preclude rapid responses to artificial, and presumably to natural, selection.

Animals↗
PubMed1967

Changing man.

The human condition is changing both culturally and biologically. Although the cultural evolution overshadows the biological, the two are connected by feedback relationships; culture has a biological foundation. Natural selection continues to operate in modern mankind, but its action ought to be supplemented by artificial selection. The problems of the management of human evolution are, however, as much sociological as they are biological. The success of any eugenical program depends on the creation of favorable conditions for human development and self-actualization. In particular, the urgency of the problem of uncontrolled overpopulation exceeds at present that of genetic improvement. Contrary to the alarmist views of some biologists, the evolutionary perspectives for the human species may be regarded as favorable, although, of course, subject to improvement. Man should be the maker of his history, including his evolutionary history. The trend toward increasing social mobility and equality of opportunity may have desirable genetic effects because of the positive assortative mating which it encourages. It makes possible the realization of many hitherto concealed genetically conditioned talents and aptitudes. Rapid progress of both molecular and organismic, Cartesian and Darwinian, biology gives hope of development of new and powerful methods of genetic engineering, control of gene action, betterment of the environment, and improved understanding of the evolutionary processes in the living world, including man.

Biological Evolution↗
PubMed1967

Of flies and men.

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Behavior↗