RESUMO
We used a balancer chromosome to recover ethylmethanesulfonate-induced recessive mutations in a targeted region of the genome of the red flour beetle (Tribolium castaneum) by the technique of chromosome extraction. The experiments reported herein constitute the first successful application of this powerful technique in the order Coleoptera. Using the balancer chromosome maxillopedia-Dachs3 (mxpDch-3), we recovered seven recessive visible variants representing seven distinct loci and several dozen recessive lethal variants representing at least five distinct loci after screening 1,607 EMS-mutagenized chromosomes. A subset of the mxpDch-3-extracted mutations were positioned on the map of the second linkage group by a series of two-, three-, and four-point crosses. The orientation of the homeotic gene complex (HOM-C) on this linkage group was also determined. With the advent of better and more varied balancer chromosomes and the concomitant improvement of chromosome extraction procedures for genetic analysis of T. castaneum, saturation mutagenesis of targeted regions of the genome is now feasible in this species.
Assuntos
Genes de Insetos , Tribolium/genética , Animais , Cromossomos , Troca Genética , Feminino , Genes Homeobox , Genes Recessivos , Ligação Genética , Variação Genética , Masculino , Mutagênese , Supressão Genética , Translocação GenéticaRESUMO
A previously unknown class of dominant, maternal-effect lethal M factors was found to be widespread in natural populations of the flour beetle, Tribolium castaneum, collected on several continents. Such factors are integrated into the host chromosomes at variable locations and show the remarkable property of self-selection by maternal-effect lethality to all hatchlings that do not inherit a copy of the factor itself. Offspring are rescued by either paternally or maternally inherited copies. The M-bearing chromosome is thereby perpetuated at the expense of its non-M homolog. M factors that map to different regions of the genome do not rescue one another's maternal-effect lethality. Factors expressing these properties are predicted to spread in a population, even in the absence of any additional selective advantage. Similar factors also occur in the related species T. confusum.