The capacity to detect nonrandom associations between restriction-map variants was examined in eight gene regions of Drosophila melanogaster (yellow-achaetescute, white, Zw, Adh, Est6, and rosy) and D. pseudoobscura (Adh and Xdh), on the basis of published population data. The statistical power from individual pairwise tests was both heterogeneous and generally low across gene regions. Sample s...

Parodontidae fish show few morphological characteristics for the identification of their representatives and chromosomal analyses have provided reliable features for determining the interrelationships in this family. In this study, the chromosomes of Apareiodon hasemani from the São Francisco River basin, Brazil, were analyzed and showed a karyotype with 2n = 54 meta/submetacentric chromosomes,...

1 The fundamental problem can be extended from p sets each consisting of a pair of variables only one of which can bc nonbasic to k sets of several variables each, only one of which can be nonbasic. To be specific, consider a system w = q f Nz, zw > 0, z > 0, where N is a p x k matrix (k < p) and the variables wl, , zu@ are partitioned into k nonempty sets SI, I = I, ., k. Let TI = SJ IJ {q}, I...

We report the discovery of highly distorted X-ray emission associated with the nearby cluster Zw 1718.1–0108, one of whose dominant members is the powerful radio galaxy 3C353. This cluster has been missed by previous X-ray cluster surveys because of its low Galactic latitude (b = 19.5◦), despite its brightness in the hard X-ray band (2–10 keV flux of 1.2 × 10erg cm s). Our optical CCD image of ...

Sex determination shows a great diversity of mechanisms, ranging from temperature and other environmental cues to strict chromosomal control over this process. In the case of genetic sex determination, this variability is linked to a similarly high variation of sex chromosome differentiation. In vertebrates the most widespread situation is that a pair of sex chromosomes differs in males and fem...

Endosymbiotic bacteria of the genus Wolbachia induce diverse reproductive alterations in their insect hosts. Wolbachia (wSca) infecting the moth Ostrinia scapulalis causes unusual male killing, in which males (genotype: ZZ) selectively die during embryonic and larval development, whereas females (genotype: ZW), in turn, selectively die when cured of infection. To gain insight into the interacti...

Karyotypic studies have shown that a ZZ/ZW sex chromosome system is used by snakes, which chromosomally resembles the ZZ/ZW system used by birds. However genetic studies have shown that SOX 3; the sex determining gene in mammals and DMRT1; which is the hypothesised sex determining gene in birds, are both located on autosomal chromosomes in the snake. Therefore it has been suggested that the sna...

We report the discovery of broad Wolf-Rayet emission lines in the Multiple Mirror Telescope (MMT) spectrum of the NW component of I Zw 18, the lowest-metallicity blue compact dwarf (BCD) galaxy known. Two broad WR bumps at the wavelengths λ4650 and λ5800 are detected indicating the presence of WN and WC stars. The total numbers of WN and WC stars inferred from the luminosities of the broad He I...

Environmental sex determination (ESD) occurs in divergent, phylogenetically unrelated taxa, and in some species, co-occurs with genetic sex determination (GSD) mechanisms. Although epigenetic regulation in response to environmental effects has long been proposed to be associated with ESD, a systemic analysis on epigenetic regulation of ESD is still lacking. Using half-smooth tongue sole (Cynogl...

Background In the leuphotrochozoan parasitic platyhelminth Schistosoma mansoni, male individuals are homogametic (ZZ) whereas females are heterogametic (ZW). To elucidate the mechanisms that led to the emergence of sex chromosomes we compared the genomic sequence and the chromatin structure of male and female individuals. As for many eukaryotes, the lower estimate for the repeat content is 40%,...