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PubMed1983

[Inversion polymorphism of the malarial mosquito Anopheles messeae. V. The interaction of different chromosomal inversions in the spatial area].

The relations between inversions of chromosome XL, 2R, 3R, 3L from 8 populations of the central part and periphery of the species area were studied. 2-, 3- and 4-factor analysis was carried out. Interaction of inversions XL1, 2R1, 3R1 in central populations (Riga, Moscow, Tomsk) was observed. The nonrandom association of definite inversional genotypes was stationary in spatial - temporary. The phylogenetic initial sequences XL0, 2R0, 3R0 display "+" interaction. The 3-factor analysis of populations of Tomsk shows: 1) interaction of inversions is more essential in males than in females; 2) the statistically significant interaction of 3-4 inversions is not always determined by the effect of 2-factor analysis; 3) the chromosome 3R has a dominance influence on the pattern of association of the multiinversional complex. These data support the hypothesis that differential selection for chromosomes with certain combinations of arrangements is mainly responsible for this phenomenon. In peripheral area populations (Syctyvkar, Irkutsk, Chita), no associations were observed (2R and 3R). When they do take place, their character is changed (Kiev - XL and 3R). This phenomenon may be explained by the influence of frequency-dependent selection.

Animals↗
PubMed2000

Chromosomal inversion polymorphism of Anopheles funestus from forest villages of South Cameroon.

The polymorphism of paracentric inversions of Anopheles funestus polytene chromosomes was studied in three villages (Nkoteng, Obala, and Simbock) located in a forest area of South Cameroon in order to analyse the genetic structure of these populations. A total of 146-210 chromatids could be scored from specimens collected over about two years. A low degree of chromosomal polymorphism was observed with two floating inversions on chromosomal arm 2 (2h and 2d), and three fixed arrangements on arms 3 (3a and 3b), and 5 (5a). Such arrangement of inversions has never been recorded elsewhere so far. The chromosome analysis indicated that the population from Obala was in Hardy-Weinberg equilibrium, whereas the samples from Nkoteng and Simbock showed a significant excess and deficit of heterokaryotypes, respectively. Significant differences in inversion frequencies on chromosomal arm 2 among villages lying in contrasting eco-climatic settings suggested an adaptive role of these inversions.

Animals↗
PubMedDate not supplied

Direct evidence for chromosomal inversion during T-cell receptor beta-gene rearrangements.

A germline T-cell receptor variable region (V beta) gene segment (V beta 14) has been mapped 10 kilobases to the 3' side of the constant region (C beta 2) gene. The V beta 14 gene segment is in an inverted transcriptional polarity relative to the diversity-region (D beta) and joining-region (J beta) gene segments and the C beta genes. Analyses of a T-cell clone (J 6.19), which has productively rearranged the V beta 14 gene segment, indicate that the productive V beta-D beta-J beta rearrangement and its reciprocal flank recombination product are linked and located at either border of a chromosomal inversion. These data demonstrate for the first time a linkage between mammalian V and C genes and verify that a functional T-cell receptor V beta gene can be constructed through a chromosomal inversion.

Amino Acid Sequence↗
PubMed1995

The evolutionary history of Drosophila buzzatii. XXXII. Linkage disequilibrium between allozymes and chromosome inversions in two colonizing populations.

Chromosome polymorphism in Drosophila buzzatii is under selection but the genes responsible for the effect of the inversions of fitness are unknown. On the other hand, there is evidence for selection on several allozyme loci but the presence of paracentric inversions on the second chromosome, where most of the polymorphic loci are located, complicates the interpretation. Studies of the associations between allozymes and inversions are thus necessary to help understand the effect of selection at both the chromosomal and allozymic level. Until now this kind of information has only been available in D. buzzatii for two loci, Est-1 and Est-2, in Australian populations. Here we describe the genetic constitution of two Old World populations, Carboneras and Colera. Emphasis has been placed on the analysis of the linkage disequilibria between the second chromosome arrangements and three allozyme loci, Est-2, Pept-2 and Aldox, located on this chromosome. In addition, the recombination frequencies between the loci, and between the loci and the inversion breakpoints, have been estimated and a genetic map of the three loci has been produced. The two populations differ in allele and arrangement frequencies, as well as in the pattern of one-locus disequilibria. Est-2 and Aldox are associated with the second chromosome arrangements in both populations. On the other hand, Pept-2 is associated with the inversions in Colera but not in Carboneras. The gametic associations among the three loci are discussed taking into account the position of these loci on the chromosome map and the lack of recombination in the heterokaryotypes.

Animals↗
PubMed1989

Chromosomal inversion patterning and population differentiation in a young insular species, Drosophila silvestris.

The recently evolved Hawaiian species Drosophila silvestris has a subdivided population structure and shows great spatial heterogeneity in chromosome inversion distributions and frequencies within its extremely limited geographic range. Pattern analysis of the 11 chromosomal polymorphisms in the context of the recently discovered morphological and behavioral divergence within the species has elucidated the history of the chromosomal differentiation. We identify four chronological groups of inversions and their probable sites of origin. Spread of the derived "3-row" bristle morphotype on the Hilo side of the Island of Hawaii has been accompanied by the acquisition of six new inversion polymorphisms. Three phylogenetically old inversions show correlations with altitude, and there are multiple cross-correlations between inversions on the same and different chromosomes, reflecting complex interaction systems. Quantification of the genetic population structure of D. silvestris by hierarchical F statistics reveals a dramatic level of genetic differentiation for an evolutionarily new species of such restricted range. This level exceeds that of older, continental Drosophila species. There is, however, minimal concordance between the chromosomal variation and the morphological-behavioral discontinuity, a consequence of the extensive cytological variation within each morphotype. Such a fragmented gene pool favors the rapid evolution and continued divergence of this insular species.

Animals↗
PubMed2003

Complete androgen insensitivity syndrome due to X chromosome inversion: a clinical report.

We have studied a patient with complete androgen insensitivity syndrome (CAIS) and a 46, inv(X),Y karyotype. The patient's mother and maternal aunt also carry the inverted X, and the mother is phenotypically normal, with a 46, inv(X),X karyotype, while a maternal aunt has CAIS with a 46,inv(X),Y karyotype. Molecular cytogenetic studies demonstrate that one of the X inversion breakpoints occurs within Xq11.2-12, which is the locus for the androgen receptor. FISH analysis demonstrated that a BAC clone containing the androgen receptor gene was disrupted by the inversion. We therefore hypothesize that disruption of the androgen receptor gene causes CAIS in this patient. This is the first report of CAIS caused by a chromosome inversion.

Adolescent↗
PubMed2003

A survey of the Anopheles funestus (Diptera: Culicidae) group of mosquitoes from 10 sites in Kenya with special emphasis on population genetic structure based on chromosomal inversion karyotypes.

We sampled Anopheles funestus Giles mosquitoes from 10 sites in Kenya to determine (1) the different members of this group present at these sites and (2) the population genetic structure of these species based on chromosomal inversion karyotypes with particular reference to the role of the Eastern arm of the Great Rift Valley and geographical distance as barriers to gene flow. Four members of this species group, namely An. funestus s.s., An. parensis, An. leesoni, and An. rivulorum, were found. An. funestus was found almost exclusively inside human dwellings while An. rivulorum was found almost exclusively outdoors. An. parensis was found both indoors and outdoors in comparable proportions. Earlier attempts to collect this group of mosquitoes from two of the sites yielded no mosquitoes, suggesting that numbers of mosquitoes change during the year, sometime reaching zero or very near zero. Significant levels of differentiation were observed among some An. funestus s.s. populations studied. Results suggest that the Rift Valley acts as a barrier to gene flow for An. funestus, but that levels of differentiation are not associated with the geographical distance between populations. The results are discussed in the light of the fact that inversions may have some adaptive significance to differences in environmental conditions.

Animals↗
PubMed2005

The structure and population genetics of the breakpoints associated with the cosmopolitan chromosomal inversion In(3R)Payne in Drosophila melanogaster.

We report here the breakpoint structure and sequences of the Drosophila melanogaster cosmopolitan chromosomal inversion In(3R)P. Combining in situ hybridization to polytene chromosomes and long-range PCR, we have identified and sequenced the distal and proximal breakpoints. The breakpoints are not simple cut-and-paste structures; gene fragments and small duplications of DNA are associated with both breaks. The distal breakpoint breaks the tolkin (tok) gene and the proximal breakpoint breaks CG31279 and the tolloid (tld) gene. Functional copies of all three genes are found at the opposite breakpoints. We sequenced a representative sample of standard (St) and In(3R)P karyotypes for a 2-kb portion of the tok gene, as well as the same 2 kb from the pseudogene tok fragment found at the distal breakpoint of In(3R)P chromosomes. The tok gene in St arrangements possesses levels of polymorphism typical of D. melanogaster genes. The functional tok gene associated with In(3R)P shows little polymorphism. Numerous single-base changes, as well as deletions and duplications, are associated with the truncated copy of tok. The overall pattern of polymorphism is consistent with a recent origin of In(3R)P, on the order of Ne generations. The identification of these breakpoint sequences permits a simple PCR-based screen for In(3R)P.

Animals↗
PubMed1982

Recombinant inversion chromosomes in phenotypically normal chickens.

Some progeny resulting from interbreeding of individuals heterozygous for a pericentric inversion of chromosome 1 in the chicken have the two complementary types of recombinant chromosomes arising from a single crossing-over within the inverted segment. These individuals are capable of reproduction. Their progeny can have one or the other of the two recombinant chromosomes or, if crossing-over occurs, either a normal or an inversion chromosome.

Animals↗
PubMed1997

Correlations among size-related traits are affected by chromosome inversions in an adaptive polymorphism in Drosophila buzzatii.

Genetic variation in correlations among size-related traits of head, thorax and wings was examined in Drosophila buzzatii, by comparing the correlation pattern of the phenotypic correlation matrix (CP-Rp) between inversion karyotypes of the second chromosome. CP-Rp differed between some karyotypes in a natural population. CP-Rp in homokaryotypic classes of wild-reared flies, but not in heterokaryotypes, differed from the whole population represented by laboratory-reared flies. Similarity in CP-Rp was highly significant for a same homokaryotype in two populations. In one of them, the chromosome is polymorphic for four inversions. In the other population, one of the inversions is almost fixed. CP-Rp was significantly similar between these populations, illustrating that similarity of CP-Rp may even occur between populations which have greatly diverged in frequencies of some genotypes affecting correlation patterns. It is suggested that chromosomal inversions are factors affecting genetic correlations among traits known to be phenotypically correlated with fitness components.

Animals↗
PubMed1998

Multiple origins of cytologically identical chromosome inversions in the Anopheles gambiae complex.

For more than 60 years, evolutionary cytogeneticists have been using naturally occurring chromosomal inversions to infer phylogenetic histories, especially in insects with polytene chromosomes. The validity of this method is predicated on the assumption that inversions arise only once in the history of a lineage, so that sharing a particular inversion implies shared common ancestry. This assumption of monophyly has been generally validated by independent data. We present the first clear evidence that naturally occurring inversions, identical at the level of light microscopic examination of polytene chromosomes, may not always be monophyletic. The evidence comes from DNA sequence analyses of regions within or very near the breakpoints of an inversion called the 2La that is found in the Anopheles gambiae complex. Two species, A. merus and A. arabiensis, which are fixed for the "same" inversion, do not cluster with each other in a phylogenetic analysis of the DNA sequences within the 2La. Rather, A. merus 2La is most closely related to strains of A. gambiae homozygous for the 2L+. A. gambiae and A. merus are sister taxa, the immediate ancestor was evidently homozygous 2L+, and A. merus became fixed for an inversion cytologically identical to that in A. arabiensis. A. gambiae is polymorphic for 2La/2L+, and the 2La in this species is nearly identical at the DNA level to that in A. arabiensis, consistent with the growing evidence that introgression has or is occurring between these two most important vectors of malaria in the world. The parallel evolution of the "same" inversion may be promoted by the presence of selectively important genes within the breakpoints.

Animals↗
PubMed2000

Spatial and temporal variations of the chromosomal inversion polymorphism of Anopheles funestus in Senegal.

The polymorphism of paracentric inversions of An. funestus polytene chromosomes was studied along a transect in Senegal in order to assess their variations at the spatial and temporal level. There was an increase in the degree of chromosomal polymorphism from the West to South-East. At the geographical level the variations in inversion frequencies were highly significant whatever the chromosomal arm considered. However, the variations in the chromosomal inversion frequencies did not change significantly over either seasons or years, except for inversion 3b in the village of Dielmo. Such geographical variability within a relatively limited area, associated to temporal stability, suggest a restricted gene flow between the populations studied, probably due to discontinuities in the An. funestus distribution and to its bioecology.

Animals↗
PubMed2003

Impact of large chromosomal inversions on the adaptation and evolution of Pseudomonas aeruginosa chronically colonizing cystic fibrosis lungs.

Pseudomonas aeruginosa chronically colonizing the lungs of cystic fibrosis (CF) patients undergoes fast evolution leading to clonal divergence. More than half of the genotypes of P. aeruginosa clone C isolates exclusively from CF lung infection exhibit large chromosomal inversions (LCIs). To analyse the impact of LCIs, as a novel mechanism of bacterial adaptation, the underlying molecular mechanism was examined. Analysis of inversion breakpoints suggested an IS6100-induced coupled insertion-inversion mechanism. A selective advantage was created by insertion of IS6100 into wbpM, pilB and mutS which leads to common CF phenotypes such as O-antigen and type IV pili deficiency and hypermutability. Speciation in bacteria is accompanied by LCIs. Therefore adaptation by LCIs that allows persistence of P. aeruginosa in the CF lung and species diversification in that new ecological niche can serve as a model for bacterial genome evolution.

Adaptation, Physiological↗
PubMed1976

Gene differences between third-chromosome inversions of Drosophila pseudobscura.

Associations of alleles of the acid phosphatase-3 locus with the different third-chromosome inversions from different populations of D. pseudoobscura are described. We observe only the allele AP-3(1.0) in the Standard and Arrowhead inversions and the allele AP-3.98 in the Santa Cruz, Treeline, Cuernavaca and the Pikes Peak arrangements. The Chiricahua gene arrangement is polymorphic.

Acid Phosphatase↗
PubMed1980

Variation in activities of amylase allozymes associated with chromosome inversions in Drosophila pseudoobscura, D. persimilis and D. miranda.

Different electrophoretic alleles of amylase show associations with particular chromosome 3 inversions in D. pseudoobscura and D. persimilis. Relative adult amylase activities were compared in 37, 37 and 10 strains of D. pseudoobscura, D. persimilis and D. miranda, respectively. Strains carrying the same electrophoretic allele were compared by crossing these lines individually to a reference strain carrying a different electrophoretic mobility allele. This procedure allows comparisons among species, inversions, electromorphs and strains for genetic variation in amylase activity. F2 analysis established that the activity variation co-segregates with the structural amylase locus. This type of variation could be due to either structural gene differences or differences in closely linked, cis-acting regulatory regions. Variation has been detected among and within electrophoretic mobility classes. Moreover, this variation is clearly nonrandom and reveals more of the genetic structure associated with the chromosomal inversion phylogeny of D. pseudoobscura and D. persimilis. ----Some of the findings are: (1) Similar electromorphs in D. pseudoobscura and D. persimilis usually show different activities. These species show nearly complete differentiation of amylase alleles, based on activities. (2) D. persimilis has the broadest range of variation in amylase activity, about four-fold between the highest and lowest alleles. D. pseudoobscura and D. miranda are also polymorphic for activity, but have more constrained ranges of variation. D. miranda alleles show on the average about four times the activity of D. pseudoobscura alleles. (3) Some association of electrophoretic mobility and activity has been found. Alleles 1.09 of D. persimilis, as well as 1.43 and 1.55 of D. miranda, have relatively high activity. It may be that these high activity alleles are part of an adaptation to cooler habitats. (4) Within electrophoretic classes, associations of activities with inversions have been found. These are especially strong in D. persimilis. The 1.00 alleles in the ST, KL, MD and WT inversions, the 0.92 allele in the ST and MD inversions and the 1.09 allele in the WT and KL inversions have levels of activities that depend upon the arrangement in which they are located. These results demonstrate that suppression of recombination in inversion heterokaryotypes can result in extensive genic divergence between inversions.

Amylases↗
PubMed1999

Are chromosomal inversions induced by transposable elements? A paradigm from the malaria mosquito Anopheles gambiae.

Chromosomal rearrangements abound in nature and can be studied in detail in organisms with polytene chromosomes. In Drosophila and in Anopheline mosquitoes most speciation processes seem to be associated with the establishment of chromosomal rearrangements, particularly of paracentric inversions. It is not known what triggers inversions in natural populations. In the laboratory inversions are commonly generated by X-rays, mutagens or after the activity of certain transposable elements (TEs). The Anopheles gambiae complex is comprised of six sibling species, each one characterized by the presence of fixed paracentric inversions on their chromosomes. Two of these, An. gambiae s.s. and An. arabiensis, are the most important vectors of human malaria and are structured into sub-populations, each carrying a characteristic set of polymorphic chromosomal inversions. We have cloned the breakpoints of the naturally occurring polymorphic inversion In(2R)d' of An. arabiensis. Analysis of the surrounding sequences demonstrated that adjacent to the distal breakpoint lies a transposable element that we called Odysseus. Characteristics of Odysseus' terminal region and its cytological distribution in different strains as well as within the same strain indicate that Odysseus is an actively transposing element. The presence of Odysseus at the junction of the naturally occurring inversion In(2R)d' suggests that the inversion may be the result of the TEs activity. Cytological evidence from Drosophila melanogaster has also implicated the hobo transposable element in the generation of certain Hawaiian endemic inversions. This picture supports the hypothesis of the important role of TEs in generating natural inversions.

Animals↗
PubMed1995

Transmission of dystrophinopathy by X-chromosome inversion.

A woman had a karyotype of 46Xinv(X)(p21.2;q26.1) and mosaicism of dystrophin-negative muscle fibers. The X-chromosome inversion was transmitted to her daughter, who had an elevated serum CK. The genetic transmission as well as the probable random inactivation of the abnormal X chromosome in this mildly affected patient distinguish this case from those of dystrophinopathy with X;autosome translocations.

Chromosome Inversion↗