| inferring the evolutionary history of drosophila americana and drosophila novamexicana using a multilocus approach and the influence of chromosomal rearrangements in single gene analyses. | the evolutionary history of closely related organisms can prove sometimes difficult to infer. hybridization and incomplete lineage sorting are the main concerns; however, genome rearrangements can also influence the outcome of analyses based on nuclear sequences. in the present study, dna sequences from 12 nuclear genes, for which the approximate chromosomal locations are known, have been used to estimate the evolutionary history of two forms of drosophila americana (drosophila americana america ... | 2008 | 18482259 |
| lack of degeneration of loci on the neo-y chromosome of drosophila americana americana. | the extent of genetic degeneration of the neo-y chromosome of drosophila americana americana has been investigated. three loci, coding for the enzymes enolase, phosphoglycerate kinase and alcohol dehydrogenase, have been localized to chromosome 4 of d. a. americana, which forms the neo-y and neo-x chromosomes. crosses between d.a. americana and d. virilis or d. montana showed that the loci coding for these enzymes carry active alleles on the neo-y chromosome in all wild-derived strains of americ ... | 1997 | 9093852 |
| genetic basis of reduced eyes in the hybrids of drosophila virilis phylad species. | structural anomalies were detected in f1 and backcross hybrids of drosophila virilis and three of its sibling species drosophila novamexicana, drosophila americana texana and drosophila americana americana. similar but not identical anomalies have been described in d. virilis x d. lummei hybrids. f1 (d. virilis x d. novamexicana) hybrids had only slight disorders in the abdominal cuticula, but 5.3% of the first backcross generation hybrids had reduced eyes. eye defects in the second generation w ... | 1992 | 1295856 |
| reduced sequence variability on the neo-y chromosome of drosophila americana americana. | sex chromosomes are generally morphologically and functionally distinct, but the evolutionary forces that cause this differentiation are poorly understood. drosophila americana americana was used in this study to examine one aspect of sex chromosome evolution, the degeneration of nonrecombining y chromosomes. the primary x chromosome of d. a. americana is fused with a chromosomal element that was ancestrally an autosome, causing this homologous chromosomal pair to segregate with the sex chromoso ... | 1999 | 10471708 |
| patterns of microsatellite variation through a transition zone of a chromosomal cline in drosophila americana. | chromosomal rearrangements have been considered as important barriers to gene flow and were often used in the delineation of species. the original taxonomic designation of drosophila americana americana and drosophila americana texana is based on the presence/absence of a centric fusion between the x- and fourth chromosomes. d. a. americana presents the derived fused state, whereas drosophila a. texana presents the freely segregating ancestral state. the degree of genetic separation between the ... | 2006 | 16823404 |
| microsatellite analysis indicates genetic differentiation of the neo-sex chromosomes in drosophila americana americana. | the neo-sex chromosomes of drosophila americana americana were formed by a centric fusion between the autosomal element b and the x chromosome. previous work has shown that the neo-y chromosome is not degenerated genetically and that there is no evidence for genetic differentiation between neo-x and neo-y chromosomes at the sequence level. to further address the genetic differentiation between the neo-sex chromosomes, microsatellites mapping to the neo-sex chromosome of d. a. americana were isol ... | 2000 | 11240628 |
| chromosomal and allelic variation in drosophila americana: selective maintenance of a chromosomal cline. | geographically structured genetic variation, as represented by clines and hybrid zones, offers unique opportunities to study adaptation and speciation in natural populations. a hybrid zone has been reported between drosophila americana americana and drosophila americana texana, two taxa that are distinguished solely by the arrangement of their x and 4th chromosomes. in this study, samples of d. americana were collected along a latitudinal transect across the inferred hybrid zone, and the frequen ... | 2002 | 11908655 |