GENOTYPIC BACKGROUND AND HETEROSIS IN DROSOPHILA PSEUDOOBSCURA

A population cage test for heterosis in Drosophila pseudoobscura.

HE existence of high levels of heterozygosity in some natural populations, perhaps as high as 10-200/0 of the genome per individual, seems by now a well-established phenomenon (see review by SPIESS 1968). Given the rather small suspected size of these populations, some explanation of how this variability is maintained seems necessary. In addition, as emphasized by LEWONTIN and HUBBY (1 966), su...

The Genotypic Control of Crossing over in Drosophila Pseudoobscura.

Effect of Environment upon the Manifestation of Heterosis and Homeostasis in Drosophila Pseudoobscura.

A NUMBER of studies involving the comparison of the F, and F, generations from crosses between geographic populations of Drosophila with the populations themselves have been carried out. In general the findings were that Fl hybrids showed a heterotic increase in Darwinian fitness over the parental populations and the F, generation showed a breakdown of heterosis. Possible explanations for this ...

Ulations of Drosophila Pseudoobscura

Most natural populations of Drosophila pseudoobscura are mixtures of individuals homozygous and heterozygous for gene arrangements in the third chromosome. The relative frequencies of the gene arrangements in populations show geographical and temporal variations. On Mount San Jacinto and in the Sierra Kevada in California, and in some localities in Texas, the temporal variations are cyclic and ...

Ancestral polymorphisms in Drosophila pseudoobscura and Drosophila miranda.

Ancestral polymorphisms are defined as variants that arose by mutation prior to the speciation event that generated the species in which they segregate. Their presence may complicate the interpretation of molecular data and lead to incorrect phylogenetic inferences. They may also be used to identify regions of the genome that are under balancing selection. It is thus important to take into acco...