Trisomy greatly enhances interstitial crossing over in a translocation heterozygote of Secale

Chromosomal rearrangements, including reciprocal translocations, may prevent recombinational transfer of genes from a donor genotype to a recipient, especially when the gene is located in an interstitial segment. The effect of trisomy of chromosome arm 1RS on recombination was studied in translocation heterozygote T248W of rye ( Secale cereale ), involving chromosome arms 1RS and 6RS. (Pro)metaphase I configuration frequencies were analyzed. Crossing over, estimated as chiasma parameters, in five genetically different euploid heterozygotes was compared with those of 10 different single arm trisomics. The addition of 1RS greatly altered the crossing over pattern around the translocation break point, with a special increase in the interstitial segment of 6RS and adjoining regions, normally hardly accessible to recombination. Furthermore, there was considerable variation between plants of closely related genotypes. Heterogeneity widens the distribution of crossing overs, including segments normally not accessible to recombination, but decreases average recombination in other segments. The extra chromosome and abnormal segregants are eliminated by using the trisomic as the pollen parent.

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THE MANIFESTATION OF CHROMOSOME REARRANGEMENTS IN UNORDERED ASCI OF NEUROSPORA

Genetics ◽

10.1093/genetics/77.3.459 ◽

1974 ◽

Vol 77 (3) ◽

pp. 459-489

Author(s):

David D Perkins

Keyword(s):

Reciprocal Translocation ◽

Chromosome Aberrations ◽

Visual Inspection ◽

Break Point ◽

Crossing Over ◽

Reciprocal Translocations ◽

Analytical Technique ◽

Large Numbers ◽

Pericentric Inversions ◽

Break Points

ABSTRACT Rapid, effective techniques have been developed for detecting and characterizing chromosome aberrations in Neurospora by visual inspection of ascospores and asci. Rearrangements that are detectable by the presence of deficient, nonblack ascospores in test crosses make up 5 to 10% of survivors after UV doses giving 10-55% survival. Over 135 rearrangements have been diagnosed by classifying unordered asci according to numbers of defective spores. (These include 15 originally identified or analyzed by other workers.) About 100 reciprocal translocations (RT's) have been confirmed and mapped genetically, involving all combinations of the seven chromosomes. Thirty-three other rearrangements generate viable nontandem duplications in meiosis. These consist of insertional translocations (IT's) (15 confirmed), and of rearrangements that involve a chromosome tip (10 translocations and 3 pericentric inversions). No inversion has been found that does not include the centromere. A reciprocal translocation was found within one population in nature. When pairs of RT's that involve the same two chromosome arms were intercrossed, viable duplications were produced if the breakpoints overlapped in such a way that pairing resembled that of insertional translocations (27 combinations).—The rapid analytical technique depends on the following. Deficiency ascospores are usually nonblack (W: "white") and inviable, while nondeficient ascospores, even those that include duplications, are black (B) and viable. Thus RT's typically produce 50% black spores, and IT's 75% black. Asci are shot spontaneously from ripe perithecia, and can be collected in large numbers as groups of eight ascospores representing unordered tetrads, which fall into five classes: 8B:0W; 6B:2W, 4B:4W, 2B:6B, 0B:8W. In isosequential crosses, 90-95% of tetrads are 8:0. When a rearrangement is heterozygous, the frequencies of tetrad classes are diagnostic of the type of rearrangement, and provide information also on the positions of break points. With RT's, 8:0 (alternate centromere segregation) = 0:8 (adjacent-1), 4:4's require interstitial crossing over in a centromere-break point interval, and no 6:2's or 2:6's are expected. With IT's, duplications are viable, 8:0 = 4:4, 6:2's are from interstitial crossing over, 0:8's or 2:6's are rare. Tetrads from RT's that involve a chromosome tip resemble those from IT's, as do tetrads from intercrosses between partially overlapping RT's that involve identical chromosome arms.—Because viable duplications and other aneuploid derivatives regularly occur among the offspring of rearrangements such as insertional translocations, care must be taken in selecting stocks, and original strains should be kept for reference.

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MITOTIC CROSSING OVER AND NONDISJUNCTION IN TRANSLOCATION HETEROZYGOTES OF ASPERGILLUS

Genetics ◽

10.1093/genetics/82.4.605 ◽

1976 ◽

Vol 82 (4) ◽

pp. 605-627

Author(s):

Etta Käfer

Keyword(s):

Selective Advantage ◽

The Other ◽

Translocation Chromosome ◽

Crossing Over ◽

Selective Marker ◽

Reciprocal Translocations ◽

Poor Growth ◽

Different Types ◽

Diploid Genotype ◽

One Step

ABSTRACT To analyze mitotic recombination in translocation heterozygotes of A. nidulans two sets of well-marked diploids were constructed, homo- or heterozygous for the reciprocal translocations T1(IL;VIIR) or T2(IL;VIIIR) and heterozygous for selective markers on IL. It was found that from all translocation heterozygotes some of the expected mitotic crossover types could be selected. Such crossovers are monosomic for one translocated segment and trisomic for the other and recovery depends on the relative viabilities of these unbalanced types. The obtained segregants show characteristically reduced growth rates and conidiation dependent on sizes and types of mono- and trisomic segments, and all spontaneously produce normal diploid sectors. Such secondary diploid types either arose in one step of compensating crossing over in the other involved arm, or—more conspicuously—in two steps of nondisjunction via a trisomic intermediate.—In both of the analyzed translocations the segments translocated to IL were extremely long, while those translocated from IL were relatively short. The break in I for T1(I;VII) was located distal to the main selective marker in IL, while that of T2(I;VIII) had been mapped proximal but closely linked to it. Therefore, as expected, the selected primary crossover from the two diploids with T2(I;VIII) in coupling or in repulsion to the selective marker, showed the same chromosomal imbalance and poor growth. These could however be distinguished visually because they spontaneously produced different trisomic intermediates in the next step, in accordance with the different arrangement of the aneuploid segments. On the other hand, from diploids heterozygous for T1(I;VII) mitotic crossovers could only be selected when the selective markers were in coupling with the translocation; these crossovers were relatively well-growing and produced frequent secondary segregants of the expected trisomic, 2n+VII, type. For both translocations it was impossible to recover the reciprocal crossover types (which would be trisomic for the distal segments of I and monosomic for most of groups VII or VIII) presumably because these were too inviable to form conidia.—In addition to the selected segregants of expected types a variety of unexpected ones were isolated. The conditions of selection used favour visual detection of aneuploid types, even if these produce only a few conidial heads and are not at a selective advantage. For T2(I;VIII) these "non-selected" unbalanced segregants were mainly "reciprocal" crossovers of the same phenotype and imbalance as the selected ones. For T1(I;VII) two quite different types were obtained, both possibly originating with loss of the small VII-Itranslocation chromosome. One was isolated when the selective marker in repulsion to T1(I;VII) was used and, without being homo- or hemizygous for the selective marker, it produced stable sectors homozygous for this marker. The other was obtained from both coupling and repulsion diploids and showed a near-diploid genotype; it produced practically only haploid stable sectors of the type expected from monosomics, 2n-1 for the short translocation chromosome.

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The M26 Hotspot of Schizosaccharomyces pombe Stimulates Meiotic Ectopic Recombination and Chromosomal Rearrangements

Genetics ◽

10.1093/genetics/149.3.1191 ◽

1998 ◽

Vol 149 (3) ◽

pp. 1191-1204 ◽

Cited By ~ 1

Author(s):

Jeffrey B Virgin ◽

Jeffrey P Bailey

Keyword(s):

Homologous Recombination ◽

Schizosaccharomyces Pombe ◽

Dna Sequences ◽

Chromosomal Rearrangements ◽

Low Frequency ◽

Repeated Sequences ◽

Crossing Over ◽

Ectopic Recombination ◽

Recombination Hotspots ◽

Integration Sites

Abstract Homologous recombination is increased during meiosis between DNA sequences at the same chromosomal position (allelic recombination) and at different chromosomal positions (ectopic recombination). Recombination hotspots are important elements in controlling meiotic allelic recombination. We have used artificially dispersed copies of the ade6 gene in Schizosaccharomyces pombe to study hotspot activity in meiotic ectopic recombination. Ectopic recombination was reduced 10–1000-fold relative to allelic recombination, and was similar to the low frequency of ectopic recombination between naturally repeated sequences in S. pombe. The M26 hotspot was active in ectopic recombination in some, but not all, integration sites, with the same pattern of activity and inactivity in ectopic and allelic recombination. Crossing over in ectopic recombination, resulting in chromosomal rearrangements, was associated with 35–60% of recombination events and was stimulated 12-fold by M26. These results suggest overlap in the mechanisms of ectopic and allelic recombination and indicate that hotspots can stimulate chromosomal rearrangements.

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Whole genome paired-end sequencing elucidates functional and phenotypic consequences of balanced chromosomal rearrangement in patients with developmental disorders

Journal of Medical Genetics ◽

10.1136/jmedgenet-2018-105778 ◽

2019 ◽

Vol 56 (8) ◽

pp. 526-535 ◽

Cited By ~ 13

Author(s):

Caroline Schluth-Bolard ◽

Flavie Diguet ◽

Nicolas Chatron ◽

Pierre-Antoine Rollat-Farnier ◽

Claire Bardel ◽

...

Keyword(s):

Developmental Disorders ◽

Chromosomal Rearrangements ◽

Position Effect ◽

Data Interpretation ◽

Major Influence ◽

Whole Genome ◽

Dna Breaks ◽

Reciprocal Translocations ◽

Gene Expression Studies ◽

Non Homologous End Joining

BackgroundBalanced chromosomal rearrangements associated with abnormal phenotype are rare events, but may be challenging for genetic counselling, since molecular characterisation of breakpoints is not performed routinely. We used next-generation sequencing to characterise breakpoints of balanced chromosomal rearrangements at the molecular level in patients with intellectual disability and/or congenital anomalies.MethodsBreakpoints were characterised by a paired-end low depth whole genome sequencing (WGS) strategy and validated by Sanger sequencing. Expression study of disrupted and neighbouring genes was performed by RT-qPCR from blood or lymphoblastoid cell line RNA.ResultsAmong the 55 patients included (41 reciprocal translocations, 4 inversions, 2 insertions and 8 complex chromosomal rearrangements), we were able to detect 89% of chromosomal rearrangements (49/55). Molecular signatures at the breakpoints suggested that DNA breaks arose randomly and that there was no major influence of repeated elements. Non-homologous end-joining appeared as the main mechanism of repair (55% of rearrangements). A diagnosis could be established in 22/49 patients (44.8%), 15 by gene disruption (KANSL1, FOXP1, SPRED1, TLK2, MBD5, DMD, AUTS2, MEIS2, MEF2C, NRXN1, NFIX, SYNGAP1, GHR, ZMIZ1) and 7 by position effect (DLX5, MEF2C, BCL11B, SATB2, ZMIZ1). In addition, 16 new candidate genes were identified. Systematic gene expression studies further supported these results. We also showed the contribution of topologically associated domain maps to WGS data interpretation.ConclusionPaired-end WGS is a valid strategy and may be used for structural variation characterisation in a clinical setting.

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The equilibrium distribution for a generalized Sankoff-Ferretti model accurately predicts chromosome size distributions in a wide variety of species

Journal of Applied Probability ◽

10.1017/s0021900200019884 ◽

2001 ◽

Vol 38 (02) ◽

pp. 324-334 ◽

Cited By ~ 1

Author(s):

Arkendra De ◽

Michael Ferguson ◽

Suzanne Sindi ◽

Richard Durrett

Keyword(s):

Stationary Distribution ◽

Simple Formula ◽

Equilibrium Distribution ◽

Size Distributions ◽

Chromosome Size ◽

Reciprocal Translocations ◽

Fitness Functions ◽

Chromosome Arm

Sankoff and Ferretti (1996) introduced several models of the evolution of chromosome size by reciprocal translocations, where for simplicity they ignored the existence of centromeres. However, when they compared the models to data on six organisms they found that their short chromosomes were too short, and their long chromosomes were too long. Here, we consider a generalization of their proportional model with explicit chromosome centromeres and introduce fitness functions based on recombination probabilities and on the length of the longest chromosome arm. We find a simple formula for the stationary distribution for our model which fits the data on chromosome lengths in many, but not all, species.

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CROSSING OVER IN A DOUBLE TRANSLOCATION IN DROSOPHILA

Canadian Journal of Genetics and Cytology ◽

10.1139/g72-015 ◽

1972 ◽

Vol 14 (1) ◽

pp. 129-137 ◽

Cited By ~ 7

Author(s):

A. S. Robinson ◽

C. F. Curtis

Keyword(s):

Drosophila Melanogaster ◽

Pest Control ◽

The Other ◽

Crossing Over ◽

Male And Female ◽

Differential Segment ◽

Translocation Heterozygote

The production and fertility of a double translocation heterozygote in Drosophila melanogaster are reported. A difference in the fertility of male and female double heterozygotes was recorded and explained on the basis of crossing over, occurring in the differential segments of female double heterozygotes, producing extra unbalanced gametes. It was shown that crossing over was absent from one differential segment but the amount of crossing over occurring in the other differential segment was measured. The possible use of multiple translocation systems for pest control is discussed with particular reference to the use of double translocation heterozygotes.

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A LINKAGE STUDY INVOLVING TWO WHEAT-RYE TRANSLOCATION CHROMOSOMES

Canadian Journal of Genetics and Cytology ◽

10.1139/g69-018 ◽

1969 ◽

Vol 11 (1) ◽

pp. 143-146 ◽

Cited By ~ 1

Author(s):

C. J. Driscoll ◽

G. D. Patil

Keyword(s):

Genetic Markers ◽

Transmission Rate ◽

Wheat Chromosome ◽

Linkage Study ◽

Linkage Test ◽

Crossing Over ◽

Complete Linkage ◽

Transmission Rates ◽

Chromosome Arm

Two wheat-rye translocation chromosomes involving the same wheat chromosome arm but different rye segments were subjected to a linkage test. Apparently no crossing over occurred between the non-homologous rye segments. The genetic markers possessed by these rye segments showed complete linkage in repulsion. The male transmission rates of the translocation chromosomes agree with those expected on the basis of the male transmission rate of each when competing with the normal wheat chromosome.

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TECHNIQUES FOR MANIPULATING CHROMOSOMAL REARRANGEMENTS AND THEIR APPLICATION TO DROSOPHILA MELANOGASTER. II. TRANSLOCATIONS

Genetics ◽

10.1093/genetics/108.3.573 ◽

1984 ◽

Vol 108 (3) ◽

pp. 573-587

Author(s):

Loring Craymer

Keyword(s):

Tandem Duplication ◽

Gene Dosage ◽

Chromosomal Rearrangements ◽

Region Of Interest ◽

Reciprocal Translocations ◽

The Third ◽

Translocation Breakpoints ◽

Inversion Breakpoints ◽

Derivatives Of ◽

Tandem Duplications

ABSTRACT Translocations have long been valued for their segregational properties. This paper extends the utility of translocations by considering recombinational derivatives of pairs of simple reciprocal translocations. Three major derivative structures are noted. One of these derivatives is suitable for use in half-tetrad experiments. A second should find use in recombining markers with translocation breakpoints. The third is an insertional-tandem duplication: it has a section of one chromosome inserted into a heterologue with a section of the latter chromosome tandemly repeated about the breaks of the insert. All of these structures are contained in "constellations" of chromosomes that regularly segregate aneuploid-1 products (informationally equivalent to nonrecombinant adjacent-1 segregants) for one of the parental translocations but do not segregate euploid products. This is in contrast to the parental T 1/T 2 constellations which segregate euploid products but not aneuploid-1 products. Methods are described for selecting translocation recombinants on the basis of this dichotomy. Several examples of translocation recombinants have been recovered with these techniques, and the recombination frequencies seem to be consistent with those observed for crossovers between inversion breakpoints. Recombinant chromosomes tend to disjoin, but it is observed that the tendency may vary according to the region involved in the recombination, and it is suggested that this difference reflects a difference in chiasmata terminalization times. Special consideration is given to insertional-tandem duplications. Large insertional-tandem duplications are useful in cytogenetic screens. Small insertional-tandem duplications are useful in gene dosage studies and other experiments that require an insert from one chromosome to another. Large duplications can be deleted to form small duplications. To generate a small insert for a specified region, it is only necessary to have one translocation with a breakpoint flanking the region of interest. The second translocation can have a breakpoint quite far from the region: an insertional-tandem duplication containing the region that has one closely flanking breakpoint can be deleted to create a smaller duplication that has two closely flanking breakpoints.

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Chromosomal abnormalities in recurrent spontaneous abortions: A retrospective study

10.22541/au.160633442.25567237/v1 ◽

2020 ◽

Author(s):

Inusha Panigrahi ◽

Mohd. Shariq ◽

Ravi Thakur ◽

Subhas Saha ◽

Gurjit Kaur

Keyword(s):

Chromosomal Rearrangement ◽

Chromosomal Abnormalities ◽

Chromosomal Rearrangements ◽

First Trimester ◽

Median Number ◽

Chromosomal Anomalies ◽

Spontaneous Abortions ◽

Reciprocal Translocations ◽

Recurrent Spontaneous Abortions ◽

Complex Chromosomal Rearrangement

Purpose: Evaluation of recurrent spontaneous abortions (RSA) can be challenging for a Obstetrician. In case of early first trimester abortions, chromosomal abnormalities can be identified as an important cause. We analysed the RSA cases followed up and diagnosed in the Genetic Clinic or Genetic Lab of 2 hospitals in the region. Methods: Those couples with 3 or more spontaneous abortions were included in the analysis. Karyotyping was one using standard protocol with G-banding and reporting as per ISCN guidelines. Results: Of 97 RSA couples, 20 showed chromosomal abnormalities, and 15 of these had balanced chromosomal rearrangements. The age ranged from 22 years to 37 years, and the median number of abortions was 4. Complex chromosomal rearrangement was seen in 2 couples, in one partner. The spectrum of chromosomal anomalies in couples with RSA is discussed here. Conclusions: Frequency of chromosomal abnormalities in RSA was higher in present study compared to previous studies. Reciprocal translocations were commonest abnormality.

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Gene conversions and crossing over during homologous and homeologous ectopic recombination in Saccharomyces cerevisiae.

Genetics ◽

10.1093/genetics/135.1.5 ◽

1993 ◽

Vol 135 (1) ◽

pp. 5-16 ◽

Cited By ~ 4

Author(s):

S Harris ◽

K S Rudnicki ◽

J E Haber

Keyword(s):

Gene Conversion ◽

Low Ph ◽

Ammonium Ion ◽

Crossing Over ◽

Hygromycin B ◽

Wild Type ◽

Reciprocal Translocations ◽

Ectopic Recombination ◽

Shared Identity ◽

The Difference

Abstract The pma1-105 mutation reduces the activity of the yeast plasma membrane H(+)-ATPase and causes cells to be both low pH and ammonium ion sensitive and resistant to the antibiotic hygromycin B. Revertants that can grow at pH 3.0 and on ammonium-containing plates frequently arise by ectopic recombination between pma1-105 and PMA2, a diverged gene that shares 85% DNA sequence identity with PMA1. The gene conversion tracts of revertants of pma1-105 were determined by DNA sequencing the hybrid PMA1::PMA2 genes. Gene conversion tracts ranged from 18-774 bp. The boundaries of these replacements were short (3-26 bp) regions of sequences that were identical between PMA1 and PMA2. These boundaries were not located at the regions of greatest shared identity between the two PMA genes. Similar results were obtained among low pH-resistant revertants of another mutation, pma1-147. One gene conversion was obtained in which the resulting PMA1::PMA2 hybrid was low pH-resistant but still hygromycin B-resistant. This partially active gene differs from a wild-type revertant only by the presence of two PMA2-encoded amino acid substitutions. Thus, some regions of PMA2 are not fully interchangeable with PMA1. We have also compared the efficiency of recombination between pma1-105 and either homeologous PMA2 sequence or homologous PMA1 donor sequences inserted at the same location. PMA2 x pma1-105 recombination occurred at a rate approximately 75-fold less than PMA1 x pma1-105 events. The difference in homology between the interacting sequences did not affect the proportion of gene conversion events associated with a cross-over, as in both cases approximately 5% of the Pma+ recombinants had undergone reciprocal translocations between the two chromosomes carrying pma1-105 and the donor PMA sequences. Reciprocal translocations were identified by a simple and generally useful nutritional test.

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