CHANGE IN THE DISTRIBUTION OF TRANSPOSABLE ELEMENTS IN ISOGENIC STRAIN — CAUSE OR CONSEQUENCE
IN DROSOPHILA MELANOGASTER SELECTION FOR QUANTITATIVE TRAITS?
L. P. Zakharenko, M. P. Perepelkina, L. A. Vasilyeva
Institute of Cytology and Genetics, Siberian Department of the RAS, Novosibirsk;
e-mail: zakharlp@bionet.nsc.ru
The distribution patterns pf hobo transposon and Dm412 retrotransposon hybridization sites on the salivary
gland polytene chromosomes from the larvae of Drosophila melanogaster isogenic strain 51, used for analyzing
the effect of transposable element (TE) transposition on the selection for quantitative traits, were studied, It was
demonstrated that at least half Dm412 hybridization sites were retained 15 years after isogenization; the frequency
of Dm412 transposition varied from 2.0·10–4 to 8.8·10–5 depending on whether the appearance of the same
hybridization sites in some individuals were regarded as independent events or as a manifestation of the sample
heterogeneity. The distribution patterns of hobo hybridization sites in two isofemale strains derived from
isogenic strain 51 differed more noticeably: the number of hobo sites in one of the derivative strains was threefold
smaller than in another and only a fraction of the sites was common. Within each derivative strain, the TE
distribution was uniform, suggesting that inbreeding had no effect on the Dm412 activity in this strain. The rates
of change in the distribution patterns of various TEs in strain 51 corresponded to their spontaneous transposition
rates. As isogenic strain accumulates the polymorphism in TE distribution without selection, the TEs are more
likely to be the markers of selection events than their inducers. Thus, when studying the effects of various environmental
factors on TE transposition even in isogenic strains, it is necessary to perform rounds of close inbreeding
to reduce the potential polymorphism.
Key words: isogenic strains, Drosophila melanogaster, transposable elements
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