Genética molecular de poblaciones de los polimorfismos de inversión en Drosophila

HASSON, E

REVISTA DE LA SOCIEDAD ENTOMOLóGICA ARGENTINA

SOCIEDAD ENTOMOLÓGICA ARGENTINA

Lugar: Mendoza; Año: 1999 vol. 58 p. 151 - 160

0373-5680

The reduction of recombination is one of the genetic con sequences of paracentric inversions. Likewise, it is widely accepted that inversion polymorphisms are selectively maintained. Inversion Payne in the left arm of the third chromosome of In(3L)P is one of four cosmopolitan inversions occurring on each of the major autosomal arms of Orosophila melanogaster. This inversion exhibits parallellatitudinal clines in several continents. The objective of the present paper is to investigate the possible effects of recombination and natural selection on the In(3L)P polimorphism. With this aim we analyzed nucleotide variation in 16 O. melanogaster and one O. simulans lines for three genomic regions located along the inverted segment: the break point (BP) regions themselves, the gene region of the heat shock protein locus (hsp-83) located close to the distal BP and the locus esterase-6 which is in the middle of the inversion. The analysis of the results showed different patterns of variation in the regions surrounding the BPs and in the center of the inversion. On one hand, in the BPs and Hsp-83, the In(3L)P lines were less variable than standard (st) lines and there are no shared polymorphisms between arrangements. Conversely, for est-6 we observed similar levels of variation in both arrangements and a high number of shared polymorphisms. In both regions, intraspecific nucleotide variation and between species divergence do not departed from neutral expectations as based on Tajima, Fu & Li, Hudson et al. and simulation tests. Our results allow us to conclude that: 1., the supression of recombination is more effective in the BPs regions; 2., the reduced polymorphism in inverted lines can be the result of selective fixations; 3., nucleotide variation do not support the view that In(3L) P is a balanced polymorphism and 4., In(3L)P is a relatively recent polymorphism that could explain the lack of significance in the neutrality tests.