Chromosomal Polymorphism Research Articles

New Oligonucleotide Probes for ND-FISH Analysis to Identify Barley Chromosomes and to Investigate Polymorphisms of Wheat Chromosomes.

Oligonucleotide probes that can be used for non-denaturing fluorescence in situ hybridization (ND-FISH) analysis are convenient tools for identifying chromosomes of wheat (Triticum aestivum L.) and its relatives. New oligonucleotide probes, Oligo-HvT01, Oligo-pTa71-1, Oligo-s120.1, Oligo-s120.2, Oligo-s120.3, Oligo-275.1, Oligo-275.2, Oligo-k566 and Oligo-713, were designed based on the repetitive sequences HVT01, pTa71, pTa-s120, pTa-275, pTa-k566 and pTa-713. All these probes can be used for ND-FISH analysis and some of them can be used to detect polymorphisms of wheat chromosomes. Probes Oligo-HvT01, Oligo-pTa71-1, Oligo-s120.3, Oligo-275.1, Oligo-k566 and Oligo-713 can, respectively, replace the roles of their original sequences to identify chromosomes of some barley (Hordeum vulgare ssp. vulgare) and the common wheat variety Chinese Spring. Oligo-s120.1, Oligo-s120.2 and Oligo-275.2 produced different hybridization patterns from the ones generated by their original sequences. In addition, Oligo-s120.1, Oligo-s120.2 and Oligo-s120.3, which were derived from pTa-s120, revealed different signal patterns. Likewise, Oligo-275.1 and Oligo-275.2, which were derived from pTa-275, also displayed different hybridization patterns. These results imply that differently arranged or altered structural statuses of tandem repeats might exist on different chromosome regions. These new oligonucleotide probes provide extra convenience for identifying some wheat and barley chromosomes, and they can display polymorphisms of wheat chromosomes.

The changes in amino acids composition of the blood associated with reproductive losses and their correction

The results of examination of women with reproductive losses (RL) in anamnesis, realized within medical-genetic consultation for explanation of the role of changes of heterochromatin (chromosome polymorphism) and the features of folate metabolism in women with RL with the perspective of individualization of preconception support on the base of determination of character of causal relation between these phenomena, were presented in the article.Aim of research: specification of the role of chromosome polymorphism and changes of amino acid composition of blood in women as the possible markers of high risk of RL.Material and methods: two groups of women were examined: I - 154 observations with obstetric anamnesis, complicated with RL and II - 32 practically healthy women with non-complicated reproductive anamnesis, who underwent preconception prophylaxis before planning of pregnancy. The genealogical anamnesis, features of the state of internal organs, genitals were studied. The special studies included cytogenetic analysis, determination of the level of free sulfur-containing amino acids (methionine, cystine, cysteine, taurine) by the method of highly effective liquid chromatography.Results: The frequency of structural changes of chromosomes in women with RL is 36,4 %. The types of slight chromosome anomalies in 3,9 % was the carriage of extremal variants of C-polymorphism; in 18,8 % – polymorphism of adjacent districts of chromosomes 13, 14, 15, 17, 21, 22; in 1,9 % – increased size of сentromere heterochromatin in chromosome; in isolated cases – the increase of linear sizes of heterochromatin districts of 9 chromosome and combination of polymorphism of adjacent districts of 15 chromosomes. In 7,1 % of cases polymorphism of adjacent districts of 21 chromosome was detected. The statistical connection between the carriage of chromosome and gene polymorphism in women with RL in anamnesis was detected. The significant difference between the main and control groups was detected only for methionine among sulfur-containing amino acids. Hyperhomocysteinemia was detected in 71,9 % of women of the main group.Conclusions: Preventive strategy as to reproductive losses must provide the timely diagnostics and correction of disorders of folate cycle that is determinative component of personalized primary prophylaxis of the disorder of reproductive function of family in the modern Ukrainian population

Значення гетерохроматину і поліморфних варіантів генів фолатного циклу у жінок з репродуктивними втратами

The article presents data from surveys of women of losses of pregnancy (LP) in history, conducted within the medical genetic counseling, given the urgency of specifying genetic factors that actually are in causal connection with the LP specification clinical effects of epigenetic variability. The objective: to clarify the meaning of the changes in women heterochromatin (chromosomal polymorphism) and polymorphic variants of genes folat cycle enzymes as potential risk factors and pathogenic primordial LP. Patients and methods. The study involved two groups of women: I - 154 observations with complicated obstetric history in LP and II - 32 healthy women with uncomplicated reproductive history, held preconception planning to prevent pregnancy. Studied genealogical history, especially of internal organs, genitalia. Special studies included cytogenetic analysis, identification of gene polymorphisms system folat cycle methylentetrahydrofolate reductase [MTHFR] (C677T, A1298C, G1793A); methionine synthase reductase [MTRR] (A66G). Results. Women with a history of LP in 36.4% identified chromosome polymorphisms (SNPs extreme variants of chromosome polymorphism) on the background of various risk alleles of polymorphic variants of genes folat cycle; 7.1% of them is a polymorphism of the 21st chromosome. These genetic features are interpreted as a significant risk factor for LP as grounds for targeted in-depth medical and genetic examination. Prevalence among women with a history of PL undifferentiated forms cjnnective tissue and mesoderm dysplasia, benign tumors and «precancerous» states, as well as the prevalence of cardiovascular and psycho-neurological disease in pedigree suggests pathogenetic link these phenomena, the role of chromosomal polymorphism and polymorphic variants of genes of pathogenic folat cycle as primordial. Conclusion. The data on the place and role of heterochromatin and gene polymorphisms folat cycle in the origin LP should be mandatory option when examining women within the medical genetic counseling. Key words: pregnancy, reproductive losses, chromosomal instability, folat cycle genes, ancestry.

Karyotype characteristics, larval morphology and chromosomal polymorphism peculiarities of Glyptotendipes salinus Michailova, 1983 (Diptera, Chironomidae) from Tambukan Lake, Central Caucasus.

Data on the karyotype characteristics, larval morphology and features of chromosomal polymorphism of a population of Glyptotendipes salinus Michailova, 1983 (Diptera, Chironomidae) from Tambukan Lake (on the northern macroslope of the central Caucasus) are presented. It was found that diagnostic larval characters of Glyptotendipes salinus from Caucasus in general are similar to those described in previous studies, but with some significant differences. By some morphological characteristics Caucasian larvae appeared to be closer to Glyptotendipes barbipes than to ones provided for European larvae of Glyptotendipes salinus by Contreras-Lichtenberg (1999). Obtained morphological data make possible to conclude that Caucasian population of Glyptotendipes salinus can be a markedly diverged population of the species, probably even subspecies. In the Caucasian population 12 banding sequences were found: two in arms A, B, C, E, and G, and one in arms D and F. Eight of these are already known for this species, and four, salA2, salB2, salEX, and salG3, are described for the first time. Genetic distances between all the previously studied populations of Glyptotendipes salinus were measured using Nei criteria (1972). The population of the central Caucasus occupies a distinct position on the dendrogram compared with populations from Altai and Kazakhstan. All the obtained morphological and cytogenetic data can indicate the plausible relative isolation and complexity of the Caucasus from the viewpoint of microevolution. More researches are required in other parts of Caucasus and other geographically distant regions for more specific allegations.

Constitutional 560.49 kb chromosome 2p24.3 duplication including the MYCN gene identified by SNP chromosome microarray analysis in a child with multiple congenital anomalies and bilateral Wilms tumor

Fewer than 100 patients with partial chromosome 2p trisomy have been reported. Clinical features are variable and depend on the size of the duplicated segment, but generally include psychomotor delay, facial anomalies, congenital heart defect, and other abnormalities. We report a 560.49 kb duplication of chromosome 2p in a 13 month-old male with hydrocephaly, ventricular septal defect, partial agenesis of the corpus callosum, and bilateral Wilms tumor. After discovery of bilateral renal masses at four months of age, the child underwent neoadjuvant chemotherapy followed by right radical nephrectomy that revealed triphasic Wilms' tumor. A needle core biopsy on one of two lesions on the left kidney also revealed Wilms tumor. A partial left nephrectomy revealed focally positive margins that necessitated left flank radiotherapy. The tumor karyotype was 46,XY,t(7;8)(q36;p11)[8]/46,XY [12] while his constitutional karyotype was 46,XY, suggesting that the t(7;8)(q36;p11) was associated with the malignancy. Single nucleotide polymorphism (SNP) chromosome microarray analysis of peripheral blood identified a maternally-inherited 560.49 kb chromosome 2p24.3 duplication that involved four OMIM genes: NBAS, DDX1, MYCNOS, and MYCN. SNP array analysis of the tumor revealed the same 2p24.3 duplication. At present, the now 5-year-old boy continues to do well without clinical or radiographic evidence of recurrent disease. This case is instructive because the child's health insurer initially denied authorization for chromosome microarray analysis (CMA), and it took more than one year before such authorization was finally granted. That initial decision to deny coverage could have had untoward health implications for this child, as the identification of constitutional MYCN duplication necessitated surveillance imaging for a number of pediatric malignancies associated with MYCN overexpression/dysregulation.

Down syndrome: from the age of characterization to the era of curative approach

Down syndrome (DS), the most prevalent autosomal disorder with a global incidence of 1 in 700 live births, was characterized in 1866 clinically and understood in 1959 genetically. However, till date DS patients are marginalized at the social cost and institutionalized for care and rehabilitation. The meiotic non-disjunction results in origin of extra 21 (Hsa21) in 95 %, whereas hereditary t(21;21) or de novo variant Robertsonian translocation contributes to the remaining. Howsoever is the origin, DS patients suffer from systemic disorders to mental retardation with a distinct phenotype, and many die in infancy or early adulthood and many at uterine age. Although the trisomy Hsa21 is the same in most of the DS-individuals, the penetrance of the resulting pathologies varies as most of them have memory and learning difficulties, craniofacial alterations and muscle hypotonia, with differential expression of congenital heart defects, leukemia or gut abnormalities. Furthermore, the severity of the defects varies greatly with varying cognitive impairment. Such variability in clinical expression could be contributed by the site of meiotic recombination of bivalents, chromosomal polymorphisms, epigenetic factors and gene dosage. Therefore, exploration has already been initiated for inactivating excess genes contributed by extra Hsa21 with a view to targeting therapy of DS. Interestingly, a remarkable result has been achieved in induced pluripotent stem cells of DS through insertion of XIST gene, which may promise a cure of future DS.

The Evolution of Orphan Regions in Genomes of a Fungal Pathogen of Wheat.

ABSTRACTFungal plant pathogens rapidly evolve virulence on resistant hosts through mutations in genes encoding proteins that modulate the host immune responses. The mutational spectrum likely includes chromosomal rearrangements responsible for gains or losses of entire genes. However, the mechanisms creating adaptive structural variation in fungal pathogen populations are poorly understood. We used complete genome assemblies to quantify structural variants segregating in the highly polymorphic fungal wheat pathogen Zymoseptoria tritici. The genetic basis of virulence in Z. tritici is complex, and populations harbor significant genetic variation for virulence; hence, we aimed to identify whether structural variation led to functional differences. We combined single-molecule real-time sequencing, genetic maps, and transcriptomics data to generate a fully assembled and annotated genome of the highly virulent field isolate 3D7. Comparative genomics analyses against the complete reference genome IPO323 identified large chromosomal inversions and the complete gain or loss of transposable-element clusters, explaining the extensive chromosomal-length polymorphisms found in this species. Both the 3D7 and IPO323 genomes harbored long tracts of sequences exclusive to one of the two genomes. These orphan regions contained 296 genes unique to the 3D7 genome and not previously known for this species. These orphan genes tended to be organized in clusters and showed evidence of mutational decay. Moreover, the orphan genes were enriched in genes encoding putative effectors and included a gene that is one of the most upregulated putative effector genes during wheat infection. Our study showed that this pathogen species harbored extensive chromosomal structure polymorphism that may drive the evolution of virulence.

Morphological variability, chromosome polymorphism, and problems of identifying individual species of gobies of the group Ponticola (Gobiidae) and assessing taxonomic relations of local populations

In connection with the problems of identification of certain species of the genus Ponticola, and especially their juveniles, morphological and genetic studies of gobies collected in the northwestern part of the Black Sea basin were carried out using literature data and museum collections. Karyological data indicate a distinct species status of western (P. odessicus) and eastern (P. eurycephalus) mushroom gobies; the range of the latter includes not only the Sea of Azov but also waters of the Black Sea coast of the Crimean Peninsula; these conclusions are supported by preliminary molecular genetic studies. Based on the obtained results of intraspecific morphological variability of species, we propose morphological characteristics for identification of adult P. syrman and P. odessicus, as well as a specific set of characteristics to identify juvenile (body length less than 50 mm) P. syrman, P. kessleri, and P. odessicus. We reveal differences in the karyotype structure of P. syrman from populations of the Sasyk Lake and the Don River, which do not differ in terms of external morphological characteristics and variability of cytochrome b haplotypes. The need for further research of phylogeography and morphological and karyological variability of P. syrman sensu lato is assumed.

The effect of chromosomal polymorphisms on the outcomes of fresh IVF/ICSI-ET cycles in a Chinese population.

Chromosomal polymorphisms (CPs) have been reported to be associated with infertility; however, their effects on the outcomes of in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) are still controversial. In this retrospective study, we aimed to evaluate the effect of CPs on IVF/ICSI-ET outcomes. To investigate whether CPs affected the outcomes of fresh IVF/ICSI-ET cycles in a Chinese population, we evaluated infertile couples with male carriers of CPs (n = 348), infertile couples with female carriers (n = 99), and unaffected couples (n = 400) who had received their first treatment cycles in our hospital between January 2013 and March 2015. CPs in either male or female carriers seemed to have adverse effects on IVF/ICSI-ET outcomes. CPs in male carriers affected outcomes mainly by decreasing the rates of fertilization, embryo cleavage, good quality embryos, clinical pregnancies, ongoing pregnancies, and deliveries as well as increasing the biochemical pregnancy rate (P < 0.05); CPs in female carriers affected outcomes only by lowering the embryo cleavage rate (P < 0.05). The mean fertilization rate of couples with male CP carriers undergoing IVF was significantly lower than that in those undergoing ICSI (61.1 versus 66.5%, respectively; P = 0.0004). Our data provide evidence for the involvement of CPs in the poor outcomes of fresh IVF/ICSI-ET cycles in a Chinese population. The use of ICSI might improve outcomes by increasing the fertilization rate for men with CPs.

Development of chromosomal markers based on next-generation sequencing: the B chromosome of the cichlid fish Astatotilapia latifasciata as a model.

BackgroundB chromosomes (Bs) are additional chromosomal elements found in a wide range of eukaryotes including fungi, plants and animals. B chromosomes are still enigmatic despite being the subject of hundreds, even thousands of reports. As yet there is no comprehensive theory for the biological role of B chromsomes thus, new studies are needed. Next-generation sequencing (NGS) holds promise for investigating classical issues in chromosome biology. NGS uses a large-scale approach that is required for advancing classical cytogenetic studies. Based on 454 sequencing data of a microdissected B chromosome and Illumina whole-genome sequencing data generated for 0B, 1B and 2B animals, we developed PCR- and qPCR-based markers for the B chromosomes of the cichlid fish Astatotilapia latifasciata (that possess 0, 1 or 2 B chromosomes).ResultsSpecific PCR primers were designed to produce two amplified fragments for B-positive samples and the control fragment for B-negative samples. Thus, PCR markers detected the presence/absence of Bs but did not provide information about the number of Bs. However, quantitative PCR (qPCR) markers clearly discriminated between 1B and 2B samples. The high copy number of the marker identified in the B chromosomes was confirmed by chromosome mapping.ConclusionsThe analysis of chromosome polymorphisms based on a NGS approach is a powerful strategy to obtain markers that detect the presence/absence of extra chromosomes or the gain or loss of genomic blocks. Further, qPCR can also provide information regarding the relative copy number of specific DNA fragments. These methods are useful to investigate various chromosome polymorphisms, including B and sex chromosomes, as well as chromosomal duplications and deletions. NGS data provide a detailed analysis of the composition of genomic regions that are thought to be present in B chromosomes.

The origin of chromosomal inversions as a source of segmental duplications in the Sophophora subgenus of Drosophila.

Chromosomal inversions can contribute to the adaptation of organisms to their environment by capturing particular advantageous allelic combinations of a set of genes included in the inverted fragment and also by advantageous functional changes due to the inversion process itself that might affect not only the expression of flanking genes but also their dose and structure. Of the two mechanisms originating inversions —ectopic recombination, and staggered double-strand breaks and subsequent repair— only the latter confers the inversion the potential to have dosage effects and/or to generate advantageous chimeric genes. In Drosophila subobscura, there is ample evidence for the adaptive character of its chromosomal polymorphism, with an important contribution of some warm-climate arrangements such as E1+2+9+12. Here, we have characterized the breakpoints of inversion E12 and established that it originated through the staggered-break mechanism like four of the five inversions of D. subobscura previously studied. This mechanism that also predominates in the D. melanogaster lineage might be prevalent in the Sophophora subgenus and contribute to the adaptive character of the polymorphic and fixed inversions of its species. Finally, we have shown that the D. subobscura inversion breakpoint regions have generally been disrupted by additional structural changes occurred at different time scales.

Karyotype analysis in large sample cases from Shenyang Women's and Children's hospital: a study of 16,294 male infertility patients

To explore that it is necessary to routinely detect chromosomes in infertile patients, we investigated peripheral blood lymphocyte karyotype in 16,294 male infertile patients in the north-east of China and analysed the incidence and type of chromosomal anomaly and polymorphism. G-banding karyotype analysis of peripheral blood lymphocytes was performed in 16,294 cases. Semen analysis was performed three times in all the men. PCR and FISH confirmed the presence of the SRY gene. The rate of chromosomal anomaly in the 16,294 male infertile patients was 4.15% (677/16,294). The rates of chromosomal anomaly were 0.24% in normal semen group, 12.6% in light oligoasthenospermia group, 4.7% in moderate-to-severe oligoasthenospermia group and 9.59% in azoospermia group. There are two male infertile patients with 45,X chromosome karyotype. One X male patient had confirmed the presence of the SRY gene and FISH analysis demonstrated its location on the p arm of chromosome 13. The other X male patient had not found SRY gene in its whole-genome DNA. Meanwhile, sperm motility is slightly oligo-asthenozoospermic at the age of 35-39 and nearly azoospermic at the age of 40-45. As the rates of chromosomal anomaly are 0.24% and 12.6% even in normal semen group and light oligoasthenospermia group, the rates of chromosomal polymorphism are 5.36% and 25.51% in normal semen group and light oligoasthenospermia group, respectively; it is necessary to explore peripheral blood lymphocyte karyotype in all infertile couples. We mentioned that Y, 1, 2, 9 and 12 chromosomes were quite important about male infertility. These findings demonstrate that autosomal retention of SRY can be submicroscopic and emphasise the importance of PCR and FISH in the genetic workup of the monosomic X male. At the same time, it suggested that male infertility might be related to meiotic disturbances with spermatogenetic arrest in Y-autosome translocations, which could result in infertility by reduction of sperm production. Last but not least, ageing is one of the factors that could reduce sperm motility and quality.

Monitoring chromosomal polymorphism inDrosophila subobscuraover 40 years

The inversion chromosomal polymorphism of Drosophila subobscura is considered to be adaptive as a result of its responses at different time scales to temperature changes. This work reports the longest-term study of chromosomal polymorphism for a single population of D. subobscura with climatic data from the collecting site itself. The chromosomal analysis of D. subobscura samples collected six times over a 40-year period at the same location and in the same seasonal interval has revealed the continuous presence of 16 common and six moderately rare chromosomal arrangements through the period. This analysis also corroborates the previously detected negative relationship between the frequencies of the standard (cold-climate) arrangement on each of its five chromosomes and temperature, as well as between a comprehensive measure of cold adaptation (the total autosomal proportion of standard arrangement) and temperature. These and previous results would support that species harboring cold- and warm-adapted polymorphic chromosomal arrangements, like D. subobscura, can rapidly respond to environmental changes.

Association of eight single nucleotide polymorphisms of chromosomes 20 and X with androgenetic alopecia among ethnic Han Chinese from Yunnan

To assess the association of 8 single nucleotide polymorphisms (SNPs) from chromosomes X and 20 with androgenetic alopecia among ethnic Han population from Yunnan province. An eight-SNP co-amplification protocol was developed for the genotyping with a SNaPshot platform. A case-control study was carried out for the 8 SNPs from chromosomes X and 20 in 115 androgenetic alopecia cases and 125 healthy controls. Statistical analysis was conducted with SPSS17.0, Haploview4.2, SHEsis and MDR software. No association was found between the two groups with regard to the 4 SNPs located on the X chromosome. The genotypic frequencies of rs2180439, rs913063 and rs1160312 were significantly different between the two groups (P < 0.05). The frequency of T allele of rs2180439 was significantly higher in the case group (P < 0.05). The frequencies of A alleles of rs913063 and rs1160312 were significantly higher in the case group (P < 0.05). The haplotypes of C-T-C-G, T-C-C-G and T-T-A-A based on rs6137444-rs2180439-rs913063-rs1160312 showed significant difference between the two groups (P <0.05). rs6137444, rs21804393 and rs1160312 have a strong association with androgenetic alopecia. The 4 SNPs located on chromosome X were all monomorphic among ethnic Hans from Yunnan. The rs6152, rs16990427, rs1352015, rs1385699 SNPs located on chromosome 20 are associated with androgenetic alopecia in the same population. Individuals with T allele of rs2180439 and A allele of rs913063 and rs1160312 are more likely to develop androgenetic alopecia.

The clinal variation of metacentric frequency in the populations of the common shrew, Sorex araneus L., in the Dnieper and Pripyat interfluve

The common shrew, Sorex araneus, is characterized by an exclusive polymorphism for Robertsonian translocations. Karyotypes of more than 70 chromosomal races of S. araneus differ from each other in composition and number of metacentrics resulting from Rb translocations which involve ten pairs of acrocentric chromosomes. The karyotype with ten pairs of acrocentric chromosomes is regarded as the initial in evolution of this species. Such acrocentric karyotype is characteristic of two chromosomal races in mountain isolates. Shrews with acrocentric karyotype have not been detected in polymorphic populations of Europe. Analysis of the chromosome polymorphism of the S. araneus in the Dnieper–Pripyat interfluve has demonstrated frequency clines for the specific metacentrics of three chromosomal races, namely the Bialowieza, Kiev, and West Dvina races. The individuals with ten acrocentric chromosome pairs were revealed for the first time in the polymorphic populations in the terminal cline parts of the Kiev and West Dvina races and in contact zone between the Bialowieza and Kiev races. Two hypotheses are being discussed to explain the clinal variation of the frequency of three race metacentrics: (1) “acrocentric peak” in contact zone of metacentric races and (2) hybridization between the metacentric races and the acrocentric race which might exist in the Dnieper basin in the past.

Tracking changes in chromosomal arrangements and their genetic content during adaptation.

There is considerable evidence for an adaptive role of inversions, but how their genetic content evolves and affects the subsequent evolution of chromosomal polymorphism remains controversial. Here, we track how life-history traits, chromosomal arrangements and 22 microsatellites, within and outside inversions, change in three replicated populations of Drosophila subobscura for 30 generations of laboratory evolution since founding from the wild. The dynamics of fitness-related traits indicated adaptation to the new environment concomitant with directional evolution of chromosomal polymorphism. Evidence of selective changes in frequency of inversions was obtained for seven of 23 chromosomal arrangements, corroborating a role for inversions in adaptation. The evolution of linkage disequilibrium between some microsatellites and chromosomes suggested that adaptive changes in arrangements involved changes in their genetic content. Several microsatellite alleles increased in frequency more than expected by drift in targeted inversions in all replicate populations. In particular, there were signs of selection in the O3+4 arrangement favouring a combination of alleles in two loci linked to the inversion and changing along with it, although the lack of linkage disequilibrium between these loci precludes epistatic selection. Seven other alleles increased in frequency within inversions more than expected by drift, but were not in linkage disequilibrium with them. Possibly these alleles were hitchhiking along with alleles under selection that were not specific to those inversions. Overall, the selection detected on the genetic content of inversions, despite limited coverage of the genome, suggests that genetic changes within inversions play an important role in adaptation.

Integrated Cytogenetic and Mitochondrial DNA Analyses Indicate That Two Different Phenotypes of Hypancistrus (L066 and L333) Belong to the Same Species.

The diversity of Hypancistrus species in the Xingu River is remarkable and the variation in color morphs represents a real challenge to taxonomists to delimit species boundaries. One of the most recognizable Hypancistrus complexes is the worm-lined species, known in the aquarium trade as King Tiger Plec in English, Hypancistrus "pão" in Portuguese or under the L-numbers L066 and L333 that represent two melanic pigment pattern phenotypes. To assess the identity of these two phenotypes, we described their karyotypes and sequenced part of the mitochondrial cytochrome oxidase I gene (DNA barcode). These fishes have 52 chromosomes (40 meta-submetacentric and 12 subtelo-acrocentric) and a strong heteromorphism in chromosome pair 21 was observed, which does not correlate with the two phenotypes or sex. DNA barcodes separated the samples analyzed from Hypancistrus zebra and other publicly available sequences of Loricariidae showing no divergence between the two phenotypes. The data set indicates that worm-lined Hypancistrus from the Xingu form a single species with clear chromosomal and melanic pigment pattern polymorphisms.

Description and plasmid characterization of the qnrD determinant in Proteeae in Wenzhou, Southern China.

Only limited information is available about the detailed characteristics of qnrD, a plasmid-mediated quinolone resistance (PMQR) gene. This study aimed to understand the distribution of qnrD and the characterization of qnrD-carrying plasmids in Proteeae. The distribution of qnrD genes was investigated by polymerase chain reaction (PCR) amplification in 203 consecutive nonduplicate clinical isolates of Proteeae collected from inpatients at the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China. The minimum inhibitory concentrations (MICs) of antibiotics were measured by agar dilution method and other PMQR determinants were also determined by PCR. qnrD was positioned via Southern hybridization and the transferability of qnrD-carrying plasmids was achieved by conjugation experiment. The genetic environment of qnrD was investigated by sequencing, and chromosomal polymorphism for qnrD-positive strains was analyzed by pulsed-field gel electrophoresis (PFGE). Forty strains carried qnrD, showing decreased fluoroquinolone susceptibility or low-level fluoroquinolone resistance. qnrD was encoded on the plasmid of about 2.7kb or 5.2kb in length, which cannot be transferred by liquid conjugation or filter mating, but can be successfully transferred by transduction. The transformants showed 62.5-300-fold increases in the MICs of quinolones compared with the recipient. The plasmids carrying qnrD showed a high similarity with that of Providencia spp. and Proteus vulgaris. PFGE analysis demonstrated that these isolates were divergent and not clone related. qnrD could have originated from Proteeae or presented in these bacteria as a reservoir; furthermore, qnrD could be transferred and spread within the same or across different bacterial species if the plasmids acquired mobile elements under antimicrobial selective pressures.

Chromosomes and speciation in tuco-tuco (Ctenomys, Hystricognathi, Rodentia)

Tuco-tucos, South American rodents of the genus Ctenomys represent an interesting model of speciation. Their strict territorial and solitary life under the earth, vast but highly fragmented habitats, low migration activity were the causes of their very fast radiation. About 60 species of this genus have been described. They are found in a variety of habitats, from the mountains of the Andes to the coastal dunes of the Atlantic, from humid steppes of Pampas to dry deserts of Chaco. Tuco-tucos have a very high level of chromosomal polymorphism and polytypism based on Robertsonian and whole-arm reciprocal translocations and inversions, and can therefore be used to test different versions of chromosomal speciation hypothesis. The classic version of this hypothesis emphasizes the sterility of the hybrids, due to incorrect or incomplete chromosome synapsis in heterozygotes for rearrangements, germ cells death, chromosome nondisjunction and the generation of unbalanced gametes. The modern version of chromosomal speciation hypothesis suggests that the reduction of gene flow across chromosomal hybrid zones is due to the suppression of recombination in hybrids around the break points of rearrangements distinguishing the parental species. Field studies have not revealed strong negative effects of chromosomal heterozygosity on the fitness of the carriers. These results cast doubt on the validity of the classic version of the hypothesis. Analysis of chromosome behavior in the meiotic prophase in the chromosomal heterozygotes revealed significant changes in the frequency and distribution of recombination: crossingover suppression around the breakpoint and chiasma distalization. These changes can modulate the flow of genes between chromosomal races and amplify the divergence which has arisen due to spatial isolation. These data confirm the recombinational model of chromosomal speciation.

Individual inversions or their combinations: which is the main selective target in a natural population of Drosophila subobscura?

It is generally accepted that chromosomal inversions have been key elements in adaptation and speciation processes. In this context, Drosophila subobscura has been, and still is, an excellent model species due to its rich chromosomal polymorphism. In this species, many analyses from natural populations have demonstrated the adaptive potential of individual inversions (and their overlapped combinations, the so-called arrangements). However, little information is available on the evolutionary role of combinations generated by inversions located in homologous and nonhomologous chromosomes. The aim of this research was to ascertain whether these combinations are also a target for natural selection. For this objective, we have studied the inversion composition of homologous and nonhomologous chromosomes from a D.subobscura sample collected in a well-studied population, Mount Avala (Serbia). No significant deviation from H-W expectations was detected, and when comparing particular karyotypic combinations, likelihood ratios close to 1 were obtained. Thus, it seems that for each pair of homologous chromosomes inversions no deviation from randomness was detected. Finally, no linkage disequilibrium was observed between inversions located in different chromosomes of the karyotype. For all these reasons, it can be assumed that, at the cytological level, the individual inversions rather than their combinations in different chromosomes are the main target of selection.