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PubMed1997

Puerperal inversion of the uterus in Nepal: case reports and review of literature.

Retrospective study of 6 cases of puerperal inversion of the uterus is being presented from 1975 to 1995 and a review of literature for 20 years of the period 1975-1995 has been summarised. In the present series, one case with acute puerperal inversion of uterus were treated by manual reposition, 2 cases of chronic puerperal inversion of uterus was treated surgically by Kustner's vaginal approach. Two cases with subacute puerperal inversion of uterus, 1 case of chronic puerperal inversion were treated by Haultain and Huntington method. Out of 241 cases of uterine inversion obtained from review of literature for last 20 years, 229 (95%) constituted puerperal and 12 (5%) were non puerperal inversions. Among puerperal inversions, 191 (83.4%) cases were of acute type and only 6 (2.62%) cases were of subacute variety. The chronic puerperal inversion constituted 32 (13.9%). Out of 63 cases of uterine inversions in India, maternal deaths were reported as 6 (9.5%) but there was no maternal death in the present series.

Adult↗

PubMedDate not supplied

Inverse agonism at heptahelical receptors: concept, experimental approach and therapeutic potential.

Inverse agonists (negative antagonists) are ligands that stabilize the inactive conformation (R) of receptors according to the two-state receptor model. The active conformation (R*) of heptahelical receptors, i.e. G protein-coupled receptors, has high affinity for G proteins. According to ternary complex models of receptor activation, the R*G complex is in equilibrium with R + G, with spontaneous activity in the absence of agonist. Inverse agonists, having a higher affinity for R, shift R*G towards R + G, decreasing the spontaneous activity of receptors. Agonists have the opposite effect, with a higher affinity for R*. Neutral antagonists have the same affinity for R and R* and compete for both agonists and inverse agonists. Inverse agonists have been recently proposed for a variety of heptahelical receptors. Methods to detect inverse agonists among antagonists are based on the determination of ligand affinity at R and R* with binding experiments, and on the modulation of G protein activity (GTP binding and hydrolysis) or of effector activity. Receptor inverse agonists, but also G protein antagonists and GTPase inhibitors, decrease spontaneous G protein activity corresponding to R*G. Receptor agonists, G protein agonists and GTPase inhibitors increase effector basal activity, but receptor inverse agonists decrease it. The therapeutic potential of inverse agonists is proposed in human diseases ascribed to constitutively active mutant receptors and may be extended to diseases related to wild-type receptor over-expression leading to the increase of R*. Some of the therapeutic effects of presently used receptor antagonists may be related to their inverse agonist properties. Inverse agonists lead to receptor upregulation, offering new approaches to tolerance and dependence to drugs.

Animals↗

PubMed2006

Class solution for inversely planned permanent prostate implants to mimic an experienced dosimetrist.

The purpose of this paper is to present a method for the selection of inverse planning parameters and to establish a set of inverse planning parameters (class solution) for the inverse planning included in a commercial permanent prostate implant treatment planning system. The manual planning of more than 750 patients since 1996 led to the establishment of general treatment planning rules. A class solution is tuned to fulfill the treatment planning rules and generate equivalent implants. For ten patients, the inverse planning is compared with manual planning performed by our experienced physicist. The prostate volumes ranged from 17 to 51 cc and are implanted with low activity 1-125 seeds. Dosimetric indices are calculated for comparison. The inverse planning needed about 15 s for each optimization (400 000 iterations on a 2.5 GHz PC). In comparison, the physicist needed about 20 min to perform each manual plan. A class solution is found that consistently produces dosimetric indices equivalent or better than the manual planning. Moreover, even with strict seed placement rules, the inverse planning can produce adequate prostate dose coverage and organ at risk protection. The inverse planning avoids implant with seeds outside of the prostate and too close to the urethra. It also avoids needles with only one seed and needles with three consecutive seeds. This reduces the risk of complication due to seed misplacement and edema. The inverse planning also uses a smaller number of needles, reducing the cause of trauma. The quality of the treatment plans is independent of the gland size and shape. A class solution is established that consistently and rapidly produces equivalent dosimetric indices as manual planning while respecting severe seed placement rules. The class solution can be used as a starting point for every patient, dramatically reducing the time needed to plan individual patient treatments. The class solution works with inverse preplanning, intraoperative inverse preplanning, and intraoperative real-time planning. This technology is not intended to replace the physicist but to accelerate the planning process, making intraoperative treatment planning more effective.

Algorithms↗

PubMed2003

Inversion for sediment geoacoustic properties at the New England Bight.

This article discusses inversions for bottom geoacoustic properties using broadband acoustic signals obtained from explosive sources. Two different inversion schemes for estimating the compressional wave speeds and attenuation are presented in this paper. In addition to these sediment parameters, source-receiver range is also estimated using the arrival time data. The experimental data used for the inversions are SUS charge explosions acquired on a vertical hydrophone array during the Shelf Break Primer Experiment conducted south of New England in the Middle Atlantic Bight in August 1996. The modal arrival times are extracted using a wavelet analysis. In the first inversion scheme, arrival times corresponding to various modes and frequencies from 10 to 200 Hz are used for the inversion of compressional wave speeds. A hybrid inversion scheme based on a genetic algorithm (GA) is used for the inversion. In an earlier study, Potty et al. [J. Acoust. Soc. Am. 108(3), 973-986 (2000)] have used this hybrid scheme in a range-independent environment. In the present study results of range-dependent inversions are presented. The sound speeds in the water column and bathymetry are assumed range dependent, whereas the sediment compressional wave speeds are assumed range independent. The variations in the sound speeds in the water column are represented using empirical orthogonal functions (EOFs). The replica fields corresponding to the unknown parameters were constructed using adiabatic theory. In the second inversion scheme, modal attenuation coefficients are calculated using modal amplitude ratios. The ratios of the modal amplitudes are also calculated using time-frequency diagrams. A GA-based inversion scheme is used for this search. Finally, as a cross check, the computed compressional wave speeds along with the modal arrival times were used to estimate the source-receiver range. The inverted sediment properties and ranges are seen to compare well with in situ measurements and historical data.

Journal Article↗

PubMed1988

The inverse problem in electrocardiography: solutions in terms of epicardial potentials.

The objective of the inverse problem in electrocardiography is to recover noninvasively regional information about intracardiac electrical events from electrical measurements on the body surface. The choice of epicardial potentials as the solution to the inverse problem is motivated by the availability of a unique epicardial potential solution for each body surface potential distribution, by the ability to verify experimentally the inverse-recovered epicardial potentials, by the proven relationship between epicardial potentials and the details of intracardiac regional events, and by the possibility of using the inverse solution as a supplement or possible replacement to clinical epicardial potential mapping prior to surgical intervention. Although, in principle, the epicardial potential distribution can be recovered from the body surface potential distribution, the inverse problem in terms of potentials is ill-posed, and naive attempts to reconstruct the epicardial potentials result in incorrect solutions which are highly oscillatory. Large deviations from the actual solution may result from inaccuracy of the data measurement, incomplete knowledge of the potential data over the entire torso, and inaccurate description of the inhomogeneous torso volume conductor. This review begins with a mathematical and qualitative description of the inverse problem in terms of epicardial potentials. The ill-posed nature of the problem is demonstrated using a theoretical boundary value problem. Effects of inaccuracies in the body surface potential data (stability estimates) are introduced, and a sensitivity analysis of geometrical and inhomogeneity parameters is presented using an analytical eccentric spheres model. Various computational methods for relating epicardial to body surface potentials, i.e., the computation of the forward transfer matrix, are described and compared. The need for regularization of the inverse recovery of epicardial potentials, resulting from the need to invert the ill-conditioned transfer matrix, is demonstrated. Several regularization techniques are compared in terms of their performance regarding noise in the data and inaccuracies in geometry and inhomogeneities. Finally, several existing, regularized inverse procedures that compute epicardial potentials from measured body surface potential data are introduced and compared. The review concludes with a section that points toward future directions for improving the quality of the inverse-reconstructed epicardial potentials. Future directions for the use of the inverse problem to obtain epicardial potential distributions noninvasively in both experimental animals and patients in a clinical se

Animals↗

PubMed2004

Acute puerperal uterine inversion.

OBJECTIVE: To determine the frequency, causes, clinical presentations, management and maternal mortality associated with acute puerperal inversion of the uterus. DESIGN: Cross-sectional analytical study. PLACE AND DURATION OF STUDY: The Department of Obstetrics and Gynaecology, Jinnah Postgraduate Medical Centre (JPMC), Karachi, over eight years period from 1st January 1995 to 31st December 2002. MATERIALS AND METHODS: All the patients who developed acute puerperal inversion of the uterus either in or outside the JPMC were included in the study. Patients of chronic uterine inversion were not included in the present study. Abdominal and vaginal examination was done to confirm and classify inversion into first, second or third degrees. RESULTS: 57036 deliveries and 36 acute uterine inversions occurred during the study period, so the frequency of uterine inversion was 1 in 1584 deliveries. Mismanagement of third stage of labour was responsible for uterine inversion in 75% of patients. Majority of the patients presented with shock, either hypovolemic (69%) or neurogenic (13%) in origin. Manual replacement of the uterus under general anaesthesia with 2% halothane was successfully done in 35 patients (97.5%). Abdominal hysterectomy was done in only one patient. There were three maternal deaths due to inversion. CONCLUSION: Proper education and training regarding placental delivery, diagnosis and management of uterine inversion must be imparted to the maternity care providers especially to traditional birth attendants and family physicians to prevent this potentially life-threatening condition.

Acute Disease↗

PubMed1987

Pericentric inversions in man: personal experience and review of the literature.

The Leuven cytogenetic centre experience on pericentric inversion in man is discussed with exclusion of the pericentric inversions of the heterochromatic blocks of chromosomes 1 and 9. In a total of 51,500 patients, referred for constitutional chromosome analysis during the period 1970-1985, pericentric inversions were found in 24 index patients. The breakpoints detected in these different pericentric inversions are summarized and compared to those found in previous reports. Bands 2p13, 2q21, 5q31, 6q21, 10q22, and 12q13 were shown to be repeatedly involved in the different studies and, furthermore, breakpoints at bands 2q11, 5p13, 5p15, 5q13, 7q11, 11q25, and 14p11 were present in this study as well as in our previous review on reciprocal autosomal translocations. In 13 familial pericentric inversions, even after exclusion of all inversion carrier probands, a 1.6:1 excess of pericentric inversion carriers versus karyotypically normal progeny was observed. While chromosomally unbalanced offspring represent 3.5% of all chromosomally investigated liveborns of the present study, 7.1% of all liveborn inversion carrier offspring presented with a mental retardation and/or multiple congenital anomalies (MR/MCA) problem. Additional chromosomal abnormalities, i.e. a 21 trisomy and an accessory small ring chromosome were observed in two pericentric inversion carriers. These data and results are discussed and compared to the data available in the literature.

Chromosome Banding↗

PubMed1976

Geographical variability in the pericentric inversion system of the grasshopper Trimerotropis pseudofasciata.

Island and mainland populations of Trimerotropis pseudofasciata from California were compared with respect to the nature and extent of their percentric inversion systems. Island populations generally have more chromosomes polymorphic for centromere position than mainland populations and a considerably higher percentage of the genome in these island populations is in a structurally heterozygous state. Thus, although geographically peripheral, the islands provide habitats capable of supporting denser and more chromosomally polymorphic populations than the mainland. Chiasmata are generally localized to terminal positions in all classes of chromosomes and do not occur in the inverted regions of inversion heterozygotes. Chiasma frequency is highest in inversion homozygotes. It is hypothesized that the inversion system in T. pseudofasciata serves the dual synergistic function of preserving allelic sequences in the inversion region intact through inversion heterozygosity and limiting the generation of variability in regions outside the inversion by increasing terminal chiasmata. Additionally, it is argued that it is the gene sequence on only the inversion chromosome that is important in Trimerotropis. This condition contrasts with the "co-adapted" pattern seen in Drosophila where the gene sequences on both chromosomes in the inversion heterozygote are simultaneously important.

Animals↗

PubMed1991

Limits of the distal inversion in the t complex of the house mouse: evidence from linkage disequilibria.

The suppression of crossing-over and the consequent linkage disequilibrium of genetic markers within the t complex of the house mouse is caused by two large and two short inversions. The inversions encompass a region that is some 15 centiMorgans (cM) long in the homologous wild-type chromosome. The limits of the proximal inversions are reasonably well-defined, those of the distal inversions much less so. We have recently obtained seven new DNA markers (D17Tu) which in wild-type chromosomes map into the region presumably involved in the distal inversions of the t chromosomes. To find out whether the corresponding loci do indeed reside within the inversions, we have determined their variability among 26 complete and 12 partial t haplotypes. In addition, we also tested the same collection of t haplotypes for their variability at five D17Leh, Hba-ps4, Pim-1, and Crya-1 loci. The results suggest that the distal end of the most distal inversion lies between the loci D17Leh467 and D17Tu26. The proximal end of the large distal inversion was mapped to the region between the D17Tu43 and Hba-ps4 loci, but this assignment is rather ambiguous. The loci Pim-1, Crya-1, and the H-2 complex, which have been mapped between the Hba-ps4 and Grr within the large distal inversion, behave as if they recombine from time to time with their wild-type homologs.

Animals↗

PubMed2006

Non-linear chromosomal inversion response in prostate after low dose X-radiation exposure.

Somatic intrachromosomal recombination can result in inversions and deletions in DNA, which are important mutations in cancer. The pKZ1 chromosomal inversion assay is a sensitive assay for studying the effects of DNA damaging agents using chromosomal inversion as a mutation end-point. We have previously demonstrated that the chromosomal inversion response in pKZ1 spleen after single low doses of X-radiation exposure does not follow the linear no-threshold dose-response model. Here, we optimised a chromosomal inversion screening method to study the effect of low dose X-radiation exposure in pKZ1 prostatic tissue. In the present study, a significant induction in inversions was observed after ultra-low doses of 0.005-0.01 mGy or after a high dose of 1000 mGy, whereas a reduction in inversions to below the sham-treated frequency was observed between 1 and 10 mGy exposure. This is the first report of a reduction to below endogenous frequency for any mutation end-point in prostate. In addition, the doses of radiation studied were at least three orders of magnitude lower than have been reported in other mutation assays in prostate in vivo or in vitro. In sham-treated pKZ1 controls and in pKZ1 mice treated with low doses of 1-10 mGy the number of inversions/gland cross-section rarely exceeded three. Up to 4 and 7 inversions were observed in individual prostatic gland cross-sections after doses < or =0.02 mGy and after 1000 mGy, respectively. The number of inversions identified in individual cross-sections of prostatic glands of untreated mice and all treated mice other than the 1000 mGy treatment group followed a Poisson distribution. The dose-response curves and fold changes observed after all radiation doses studied were similar in spleen and prostate. These results suggest that the pKZ1 assay is measuring a fundamental response to DNA damage after low dose X-radiation exposure which is independent of tissue type.

Animals↗

PubMed2006

Assaying chromosomal inversions by single-molecule haplotyping.

Inversions are an important form of structural variation, but they are difficult to characterize, as their breakpoints often fall within inverted repeats. We have developed a method called 'haplotype fusion' in which an inversion breakpoint is genotyped by performing fusion PCR on single molecules of human genomic DNA. Fusing single-copy sequences bracketing an inversion breakpoint generates orientation-specific PCR products, exemplified by a genotyping assay for the int22 hemophilia A inversion on Xq28. Furthermore, we demonstrated that inversion events with breakpoints embedded within long (>100 kb) inverted repeats can be genotyped by haplotype-fusion PCR followed by bead-based single-molecule haplotyping on repeat-specific markers bracketing the inversion breakpoint. We illustrate this method by genotyping a Yp paracentric inversion sponsored by >300-kb-long inverted repeats. The generality of our methods to survey for, and genotype chromosomal inversions should help our understanding of the contribution of inversions to genomic variation, inherited diseases and cancer.

Chromosome Inversion↗

PubMed2003

Evolutionary genomics of inversions in Drosophila pseudoobscura: evidence for epistasis.

Drosophila pseudoobscura harbors a rich polymorphism for paracentric inversions on the third chromosome, and the clines in the inversion frequencies across the southwestern United States indicate that strong natural selection operates on them. Isogenic inversion strains were made from isofemale lines collected from four localities, and eight molecular markers were mapped on the third chromosome. Nucleotide diversity was measured for these loci and formed the basis of an evolutionary genomic analysis. The loci were differentiated among inversions. The inversions did not show significant differences among populations, however, likely the result of extensive gene flow among populations. Some loci had significant reductions in nucleotide diversity within inversions compared with interspecies divergence, suggesting that these loci are near inversion breakpoints or are near targets of directional selection. Linkage disequilibrium (LD) levels tended to decrease with distance between loci, indicating that some genetic exchange occurs among gene arrangements despite the presence of inversions. In some cases, however, adjacent genes had low levels of interlocus LD and loosely linked genes had high levels of interlocus LD, suggesting strong epistatic selection. Our results support the hypothesis that the inversions of D. pseudoobscura have emerged as suppressors of recombination to maintain positive epistatic relationships among loci within gene arrangements that developed as the species adapted to a heterogeneous environment.

Animals↗

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↗

PubMed2003

The foldback-like transposon Galileo is involved in the generation of two different natural chromosomal inversions of Drosophila buzzatii.

Chromosomal inversions are the most common type of genome rearrangement in the genus Drosophila. Although the potential of transposable elements (TEs) for generating inversions has been repeatedly demonstrated in the laboratory, little is known on their role in the generation of natural inversions, which are those effectively contributing to the adaptation and/or evolution of species. We have cloned and sequenced the two breakpoints of the polymorphic inversion 2q7 of D. buzzatii. The sequence analysis of the breakpoint regions revealed the presence in the inverted chromosomes of large insertions, formed by complex assemblies of transposons, that are absent from the chromosomes without the inversion. Among the transposons inserted, the Foldback-like element Galileo, that was previously found responsible of the generation of the widespread inversion 2j of D. buzzatii, is present at both 2q7 breakpoints and is the most likely inducer of the inversion. A detailed study of the nucleotide and structural variation in the breakpoint regions of six chromosomal lines with the 2q7 inversion detected no nucleotide differences between them, which suggests a monophyletic and recent origin. In contrast, a remarkable degree of structural variation was observed in the same six chromosomal lines. It thus appears that the two breakpoints of the inverted chromosomes have become genetically unstable hotspots, as was previously found for the 2j inversion breakpoints. The possibility that this instability is caused by structural properties of Foldback elements is discussed.

Animals↗

PubMed2025

Cosmopolitan inversions have a major impact on trait variation and the power of different GWAS approaches to identify associations.

The ability of genomic inversions to reduce recombination and generate linkage can have a major impact on genetically based phenotypic variation in populations. However, the increase in linkage associated with inversions can create hurdles for identifying associations between loci within inversions and the traits they impact. As a consequence, the role of inversions in mediating genetic variation in complex traits remains to be fully understood. This study uses the fruit fly Drosophila melanogaster to investigate the impact of inversions on trait variation. We tested the effects of common inversions among a diverse assemblage of traits including aspects of behavior, morphology, and physiology, and identified that the cosmopolitan inversions In(2L)t and In(3R)Mo are associated with many traits. We compared the ability of different approaches of accounting for relatedness and inversion presence during genome-wide association to identify signals of association with SNPs. We report that commonly used association methods are underpowered within inverted regions, while alternative approaches such as leave-one-chromosome-out improve the ability to identify associations. In all, our research enhances our understanding of inversions as components of trait variation and provides insight into approaches for identifying genomic regions driving these associations.

Drosophila melanogaster↗

PubMed2006

Int22h-related inversions causing hemophilia A: a novel insight into their origin and a new more discriminant PCR test for their detection.

BACKGROUND: Intrachromosomal, homologous recombination of the duplicon int22h-1 with int22h-2 or int22h-3 causes inversions accounting for 45% of severe hemophilia A, hence the belief that int22h-2 and int22h-3 are in opposite orientation to int22h-1. However, inversions involving int22h-2 are five times rarer than those involving its virtually identical copy: int22h-3. Recent sequencing has indicated that int22h-2 and int22h-3 form the internal part of the arms of an imperfect palindrome so that int22h-2, in the centromeric arm, has the same orientation as int22h-1 and, upon recombination with int22h-1, should produce deletions and duplications but not inversions. AIM: This work aims to provide rapid tests for all the mutations that can result from recombinations between the int22h sequences and to investigate whether int22h-2-related inversions causing hemophilia A arise in chromosomes, where the arms of the palindrome have recombined so that int22h-2 and int22h-3 swap places and orientation. PATIENTS/METHODS: Twenty patients with int22h-related inversions were examined together with a control and inversion carriers using reverse transcription-polymerase chain reaction (RT-PCR), long-range PCR and sequencing. RESULTS AND CONCLUSIONS: Analysis of mRNA in patients and a control provided evidence confirming the palindromic arrangement of int22h-2 and int22h-3 and the proposed inversion polymorphism that allows int22h-2 to be in the telomeric arm of the palindrome and in opposite orientation to int22h-1. New long-range PCR reactions were used to develop a single tube test that detects and discriminates inversions involving int22h-2 or int22h-3 and a two-tube test that can distinguish inversions, deletions, and duplications due to recombination between int22h sequences.

Base Sequence↗

PubMed2002

Inversions over the terminus region in Salmonella and Escherichia coli: IS200s as the sites of homologous recombination inverting the chromosome of Salmonella enterica serovar typhi.

Genomic rearrangements (duplications and inversions) in enteric bacteria such as Salmonella enterica serovar Typhimurium LT2 and Escherichia coli K12 are frequent (10(-3) to 10(-5)) in culture, but in wild-type strains these genomic rearrangements seldom survive. However, inversions commonly survive in the terminus of replication (TER) region, where bidirectional DNA replication terminates; nucleotide sequences from S. enterica serovar Typhimurium LT2, S. enterica serovar Typhi CT18, E. coli K12, and E. coli O157:H7 revealed genomic inversions spanning the TER region. Assuming that S. enterica serovar Typhimurium LT2 represents the ancestral genome structure, we found an inversion of 556 kb in serovar Typhi CT18 between two of the 25 IS200 elements and an inversion of about 700 kb in E. coli K12 and E. coli O157:H7. In addition, there is another inversion of 500 kb in E. coli O157:H7 compared with E. coli K12. PCR analysis confirmed that all S. enterica serovar Typhi strains tested, but not strains of other Salmonella serovars, have an inversion at the exact site of the IS200 insertions. We conclude that inversions of the TER region survive because they do not significantly change replication balance or because they are part of the compensating mechanisms to regain chromosome balance after it is disrupted by insertions, deletions, or other inversions.

Chromosome Inversion↗

PubMed2005

Sperm studies in heterozygote inversion carriers: a review.

The risk of producing unbalanced gametes in heterozygous inversion carriers mostly depends on the occurrence of recombination events within the inverted segment. Recombination determines the possibility of producing chromosomes with duplications/deficiencies (pericentric inversions) or with duplications/deficiencies which furthermore appear as dicentric and acentric fragments (paracentric inversions). In this work, a general description of the close relationship between the occurrence of crossovers in pericentric and paracentric inversions and the final segregation outcome is presented. After this introduction, a compilation of inversion segregation data and interchromosomal effect results from previously published sperm studies have been reviewed. Segregation results indicate a great heterogeneity in the percentage of unbalanced gametes, from 0 to 37.38%. The size of the inverted segments and their proportion in the chromosome are two parameters closely related with the incidence of recombination (P < 0.0001; using a quadratic model and Pearson's correlation test). These results suggest that the production of a significant level of unbalanced gametes would require a minimum inversion size of 100 Mbp and the inversion of at least 50% of the chromosome. Interchromosomal effects are seldom observed in chromosomal inversions. Finally, implications of the meiotic behavior of the inversions in the progeny of the carriers and the incorporation of sperm FISH segregation analysis for reproductive genetic counseling are discussed.

Chromosome Inversion↗