Nature has required species to adapt themselves to their environment through changes in their genetic makeup. These changes, known as mutations, can come about by various means, from a base substitution in a DNA molecule to major alterations in one or more chromosomes. Most often, these mutations are prejudicial and are eliminated by natural selection, but they can be favourable increasing the carrier's capacity for survival and reproduction and, in time, lead to new species.

One of the organisms which scientists have studied in great depth with regard to these changes is the Drosophila fly. This organism has giant sized chromosomes in the salivary glands of its larvae which are relatively easy to view with a microscope. This characteristic make it an excellent source for studying genetic changes that take place in the course of evolution. One of the most typical genetic changes in the Drosophila type species are the chromosomal inversions. In these, a segment of the DNA molecule, which corresponds to a chromosome, adopts an inverted orientation with regard to the original order. Despite many years of study, the molecular mechanisms that generate these inversions have remained unknown.

Researchers from the Department of Genetics and Microbiology at the Universitat Autònoma de Barcelona (UAB), in collaboration with a researcher from the University of Chicago, have demonstrated that the origin of natural chromosomal inversions present in the Drosophila are found in small independent DNA sequences. These sequences are known as transposons, or transposable elements, that are able to reproduce themselves and insert themselves freely in different points of the chromosomes. Transposons were discovered some fifty years ago but the implications of these with regard to cellular operations have only recently begun to be uncovered.

The research team is made up of Mario Cáceres, José Mara Ranz, Antonio Barbadilla
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Contact: Alfredo Ruiz
ibge5@cc.uab.es
34-93-581-27-29
Universitat Autonoma de Barcelona
19-Jul-1999