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Genetical Research

Table of Contents - 2006 - Volume 87, Issue 03  


On the location of the gene(s) harbouring the advantageous variant that maintains the X/4 fusion of Drosophila americana

CRISTINA P. VIEIRA a1, ANDRÉ ALMEIDA a1, JOÃO DANIEL DIAS a1 and JORGE VIEIRA a1c1
a1 Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal

Article author query
vieira cp   [PubMed][Google Scholar] 
almeida a   [PubMed][Google Scholar] 
daniel dias j   [PubMed][Google Scholar] 
vieira j   [PubMed][Google Scholar] 

Abstract

Weak selection is maintaining the Drosophila americana X/4 fusion chromosomal frequency cline. The gene(s) harbouring the advantageous variant(s) that is responsible for the establishment and maintenance of this chromosomal frequency gradient must be located in a region of the X and/or 4th chromosome that is genetically isolated between the X/4 fusion and non-fusion forms. The limits of these regions must thus be determined before an attempt is made to identify these genes. For this purpose, the correspondence between the D. virilis X and 4th chromosome genome scaffolds sequence and the D. americana gene order was established. Polymorphism levels and patterns at seven genes located at the base of the D. americana X chromosome, as well as three genes located at the base of the 4th chromosome, were analysed. The data suggest that the D. americana X/4 fusion is no more than 29000 years old. At the base of the X chromosome, there is suppression of recombination within X/4 fusion and non-fusion chromosomes, and little recombination between the two chromosomal forms. Apparent fixed silent and replacement differences are found in three of seven genes analysed located at the base of the X chromosome. There is no evidence for suppression of recombination between fusion and non-fusion chromosomes at the base of the 4th chromosome. The advantageous variant responsible for the establishment in frequency and maintenance of the X/4 fusion is thus inferred to be in the D. americana X centromere–inversion Xc basal breakpoint region.

(Received June 9 2005)
(Revised October 10 2005)
(Revised March 9 2006)


Correspondence:
c1 Molecular Evolution Laboratory, Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823 Porto 4150-180, Portugal. Tel: +351 22 6074900. Fax: +351 22 6099157. e-mail: jbvieira@ibmc.up.pt

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