scholarly journals THE MANIFESTATION OF CHROMOSOME REARRANGEMENTS IN UNORDERED ASCI OF NEUROSPORA

Genetics ◽  
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.

scholarly journals HIGH RATES OF OCCURRENCE OF SPONTANEOUS CHROMOSOME ABERRATIONS IN DROSOPHILA MELANOGASTER

Genetics ◽  
1976 ◽  
Vol 83 (2) ◽  
pp. 409-422
Author(s):  
Osamu Yamaguchi ◽  
Ricardo A Cardellino ◽  
Terumi Mukai
Keyword(s):  
Chromosome Aberrations ◽  
Gene Arrangement ◽  
Reciprocal Translocations ◽  
Lethal Effects ◽  
Recessive Lethal ◽  
The Third ◽  
Lethal Mutations ◽  
Pericentric Inversions ◽  
Break Points ◽  
Spontaneous Chromosome

ABSTRACT Spontaneous mutations were accumulated for 40 generations in 140 unrelated second chromosomes with the standard gene arrangement. These were extracted from the same population by using the marked inversion technique, and the following findings were obtained: (1) In 42 out of the 140 chromosome lines, chromosome aberrations were detected by examining the salivary gland chromosomes: 40 paracentric and 15 pericentric inversions, 2 reciprocal translocations between the second and the third chromosomes, and 6 transpositions. (2) In 63 out of the 90 originally lethal-free lines, recessive lethal mutations occurred. (3) There were only 3 lines that acquired chromosome aberrations (inversions) with no lethal effects in the homozygous condition. (4) In a comparison of these results with those of the (CH), (PQ), and (RT) chromosomes in which no chromosome aberrations occurred after accumulating mutations for 22058 chromosome·generations (Yamaguchi and Mukai 1974), it was concluded that some of these 140 chromosomes carried a kind of mutator. (5) The frequency of mutator-carrying chromosome lines was estimated to be 0.66 on the basis of the distribution of the break-points on the chromosome lines and the frequency of lines that acquired neither recessive lethal mutations nor chromosome aberrations. Thus, the average number of breaks per mutator-carrying chromosome was estimated to be about 0.19/generation. On the basis of these estimates, the nature of the mutator factor was discussed.

Three-to-one segregation from reciprocal translocation quadrivalents in Neurospora and its bearing on the interpretation of spore-abortion patterns in unordered asci

Genome ◽  
1995 ◽  
Vol 38 (4) ◽  
pp. 661-672 ◽  
Author(s):  
David D. Perkins ◽  
Namboori B. Raju
Keyword(s):  
Frequency Characteristic ◽  
Meiotic Division ◽  
Reciprocal Translocation ◽  
Visual Inspection ◽  
Chromosome Rearrangement ◽  
The Other ◽  
Sequence Information ◽  
Crossing Over ◽  
Distal Half ◽  
Basal Half

In Neurospora, viable ascospores become black (B) when mature, whereas ascospores that are deficient for a chromosome segment are inviable and usually fail to blacken. The presence of a chromosome rearrangement can be recognized and the type of rearrangement can usually be inferred by visual inspection of asci. When a cross is heterozygous for a reciprocal translocation, asci with eight black ascospores (8B:0W) and asci with eight abortive unpigmented ("white" (W)) ascospores (0B:8W) are theoretically produced in equal numbers if homologous centromeres are equally likely to segregate from the quadrivalent in alternate or adjacent modes. In addition, 4B:4W asci are produced with a frequency characteristic of each reciprocal translocation. Information on ascospore-abortion patterns in Neurospora crassa has come predominantly from unordered ascospore octads ejected from the perithecium. Unordered asci of the 4B:4W type were initially presumed to originate by interstitial crossing over in a centromere-breakpoint interval and their frequency was used as a predictor of centromere locations. However, 4B:4W asci can result not only from interstitial crossing over but also from nondisjunction of centromeres at the first meiotic division, which leads to 3:1 segregation. Ordered linear 4B:4W asci retain the sequence information necessary for distinguishing one mode of origin from the other but unordered asci do not. Crossing over results in one abortive duplication–deficiency ascospore pair in each opposite half of a linear ascus, while 3:1 segregation places both abortive ascospore pairs together, either in the distal half or the basal half of the ascus. In the present study, perithecia were opened and intact linear asci were examined in crosses heterozygous for a varied sample of translocations. Three-to-one segregation rather than interstitial crossing over is apparently the main cause of 4B:4W asci when breakpoints are near centromeres, whereas crossing over is responsible for most or all 4B:4W asci when breakpoints are far-distal. Three-to-one segregation does not impair the usefulness of ejected unordered asci for detecting chromosome rearrangements. Ejected octads are superior to ordered linear asci for distinguishing one type of rearrangement from another, because ascus ejection from the perithecium does not occur until viable ascospores are fully pigmented, enabling true 0B:8W asci to be distinguished from those with eight immature ascospores.Key words: ascospore abortion, ascus analysis, Neurospora, nondisjunction, reciprocal translocation, three-to-one segregation.

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

Genome ◽  
2012 ◽  
Vol 55 (1) ◽  
pp. 15-25 ◽  
Author(s):  
J. Sybenga ◽  
H.M. Verhaar ◽  
D.G.A. Botje
Keyword(s):  
Secale Cereale ◽  
Extra Chromosome ◽  
Chromosomal Rearrangements ◽  
Break Point ◽  
Pollen Parent ◽  
Crossing Over ◽  
Reciprocal Translocations ◽  
Translocation Heterozygote ◽  
Chromosome Arm ◽  
Donor Genotype

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.

scholarly journals MITOTIC CROSSING OVER AND NONDISJUNCTION IN TRANSLOCATION HETEROZYGOTES OF ASPERGILLUS

Genetics ◽  
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.

NEW DUPLICATION-GENERATING INVERSIONS IN NEUROSPORA

1969 ◽  
Vol 11 (3) ◽  
pp. 622-638 ◽  
Author(s):  
Barbara C. Turner ◽  
Cecile W. Taylor ◽  
David D. Perkins ◽  
Dorothy Newmeyer
Keyword(s):  
Mating Type ◽  
Break Point ◽  
Low Fertility ◽  
Type Locus ◽  
Complementary Product ◽  
Single Crossing ◽  
Group I ◽  
Distinctive Morphology ◽  
Phenotype Characteristic ◽  
Break Points

Inversion In(ILR)NM176 has one break point at the extreme right end of linkage group I and the other distal to mating type in the left arm. In crosses of Inversion × Normal the products of single crossing over within the inversion are complementary duplication-deficiency classes. One crossover product is viable, with a large segment of IL duplicated and the dispensable right tip presumably deficient. This class has low fertility and distinctive morphology. The complementary product has a large deficiency which results in a pair of white, inviable ascospores. Single exchanges within the heterozygous inversion thus produce asci with 6 Black: 2 White spores; four-strand double exchanges produce 4 B:4 W; and non-exchanges produce asci with 8 B:0 W. Approximate mapping of break points was accomplished by three-point crosses. Precise placement of the left break point between ser-3 and un(55701t), just left of mating type, is based on coverage of markers by the heterozygous duplication. No crossover has been obtained between mating type and the break point, despite extensive efforts. In(ILR)NM176 differs from the inversion In(ILR)H4250 described by Newmeyer and Taylor (1967) in one main respect: the mating type locus is included in the inverted segment of NM176. Consequently, when duplications are generated, the progeny are unisexual and do not have the unstable inhibited phenotype characteristic of H4250 duplication progeny, which are heterozygous for the mating type alleles A and a. Three other inversions which originated independently of In(ILR)NM176 resemble it closely and have similar or identical break points.

Absorbance errors from using pieced-together rotors in the Roche Cobas-Bio centrifugal analyzer.

1987 ◽  
Vol 33 (7) ◽  
pp. 1198-1199
Author(s):  
W G Miller ◽  
E K Armitage
Keyword(s):  
Break Point ◽  
T Test ◽  
Random Errors ◽  
Significant Difference ◽  
Break Points ◽  
The Difference ◽  
Roche Cobas

Abstract Two Cobas-Bio analyzers were found to have significantly increased imprecision, owing to absorbance errors, when we used rotors pieced together from segments of four to 10 cuvets. The difference in CV between whole/unbroken and four-cuvet or 10-cuvet segment rotors was significant by Student's unpaired t-test (P = 0.038 and less than 0.0001, respectively) and by the Mann-Whitney U test (P less than 0.0001 for either). Pieced-together rotors were found to have plastic fragments in some cuvets, both adjacent to the break points and in other positions within the segment. There was no significant difference in delta A between adjacent cuvets at break positions or in between break positions by unpaired t-test (P = 0.214) or by the Mann-Whitney U test (P = 0.235). There was a significant difference by either test (P less than 0.0001) for the delta A between adjacent cuvets in broken rotors and those in whole/unbroken rotors. We conclude that random errors in absorbance are observed both in cuvets adjacent to break positions and in cuvets removed from the break point when pieced-together rotors are used.

RADIATION INDUCED RECIPROCAL TRANSLOCATIONS AND INVERSIONS IN ANOPHELES ALBIMANUS

1982 ◽  
Vol 24 (2) ◽  
pp. 177-188 ◽  
Author(s):  
P. E. Kaiser ◽  
J. A. Seawright ◽  
M. Q. Benedict ◽  
S. Narang ◽  
S. G. Suguna
Keyword(s):  
X Rays ◽  
Anopheles Albimanus ◽  
Reciprocal Translocations ◽  
Pericentric Inversions ◽  
Radiation Induced ◽  
Homozygous Translocation ◽  
Paracentric Inversions ◽  
Heterozygous Translocation

Reciprocal translocations and inversions were induced in Anopheles albimanus Wiedemann by irradiation of males with X rays. A total of 1669 sperm were assayed, and 175 new aberrations were identified as follows: 102 reciprocal translocations (67 autosomal and 35 sex-linked), 45 pericentric inversions, and 28 paracentric inversions. Eleven of the translocations were nearly whole-arm interchanges, and these were selected for the construction of "capture systems" for compound chromosomes. Two double-heterozygous translocation strains and four homozygous translocation strains were established. Anopheles albimanus females were irradiated, and a pseudolinkage scheme involving mutant markers was employed to identify reciprocal translocations. The irradiation of females was very inefficient: only one translocation was recovered from 1080 ova tested.

The Effect of Universal Decolonization With Screening in Critical Care to Reduce MRSA Across an Entire Hospital

2017 ◽  
Vol 38 (4) ◽  
pp. 430-435 ◽  
Author(s):  
Craig W. Bradley ◽  
Martyn A. C. Wilkinson ◽  
Mark I. Garvey
Keyword(s):  
Time Series ◽  
United Kingdom ◽  
Time Series Analysis ◽  
Regression Models ◽  
Kernel Regression ◽  
Break Point ◽  
University Hospitals ◽  
Series Analysis ◽  
The United Kingdom ◽  
Break Points

OBJECTIVETo describe the effect of universal methicillin-resistant Staphylococcus aureus (MRSA) decolonization therapy in a large intensive care unit (ICU) on the rates of MRSA cases and acquisitions in a UK hospital.DESIGNDescriptive study.SETTINGUniversity Hospitals Birmingham (UHB) NHS Foundation Trust is a tertiary referral teaching hospital in Birmingham, United Kingdom, that provides clinical services to nearly 1 million patients every year.METHODSA break-point time series analysis and kernel regression models were used to detect significant changes in the cumulative monthly numbers of MRSA bacteremia cases and acquisitions from April 2013 to August 2016 across the UHB system.RESULTSPrior to 2014, all ICU patients at UHB received universal MRSA decolonization therapy. In August 2014, UHB discontinued the use of universal decolonization due to published reports in the United Kingdom detailing the limited usefulness and cost-effectiveness of such an intervention. Break-point time series analysis of MRSA acquisition and bacteremia data indicated that break points were associated with the discontinuation and subsequent reintroduction of universal decolonization. Kernel regression models indicated a significant increase (P<.001) in MRSA acquisitions and bacteremia cases across UHB during the period without universal decolonization.CONCLUSIONWe suggest that routine decolonization for MRSA in a large ICU setting is an effective strategy to reduce the spread and incidence of MRSA across the whole hospital.Infect Control Hosp Epidemiol 2017;38:430–435

scholarly journals Fusional Vergence Detected by Prism Bar and Synoptophore in Chinese Childhood Intermittent Exotropia

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Tao Fu ◽  
Jing Wang ◽  
Moran Levin ◽  
Qing Su ◽  
Dongguo Li ◽  
...  
Keyword(s):  
Break Point ◽  
Chinese Children ◽  
Intermittent Exotropia ◽  
Link Type ◽  
Control Score ◽  
Significant Difference ◽  
Angle Of Deviation ◽  
Break Points

Purpose. To measure the changes in fusional vergence in Chinese children with intermittent exotropia (IXT) and the association with the control of IXT.Methods. Ninety-two patients with IXT (8–15 years old) were compared with 86 controls. Exodeviation control was evaluated using the Revised Newcastle Control Score. Angle of deviation was measured using prism and alternate cover testing at distance and near. Fusional vergence was measured using prism bar and synoptophore. This study was registered withChiCTR-RCC-13003920.Results. Using prism bar, convergence break points were lower whereas divergence break points were higher in children with IXT at distance (P<0.001) and near (P<0.001) compared with controls. There was no significant difference in mean divergence amplitudes between the two groups when testing using a synoptophore (P=0.53). In children with IXT, the distance between recovery point and break point in both convergence (distance:P=0.02; near:P=0.02) and divergence (distance:P<0.001; near:P<0.001) was larger than controls when detected by prism bar and synoptophore (convergence:P=0.005; divergence:P=0.006).Conclusions. Children with IXT have reduced convergence amplitudes as detected by both prism bar and synoptophore.

A rule-based phrase parser for real-time text-to-speech synthesis

1995 ◽  
Vol 1 (2) ◽  
pp. 191-212 ◽  
Author(s):  
Joan Bachenko ◽  
Eileen Fitzpatrick ◽  
Jeffrey Daugherty
Keyword(s):  
Real Time ◽  
Hard Of Hearing ◽  
Speech Synthesis ◽  
Break Point ◽  
Linguistic Context ◽  
Text To Speech ◽  
Rule Based ◽  
Front End ◽  
Text To Speech Synthesis ◽  
Break Points

AbstractText-to-speech systems are currently designed to work on complete sentences and paragraphs, thereby allowing front end processors access to large amounts of linguistic context. Problems with this design arise when applications require text to be synthesized in near real time, as it is being typed. How does the system decide which incoming words should be collected and synthesized as a group when prior and subsequent word groups are unknown? We describe a rule-based parser that uses a three cell buffer and phrasing rules to identify break points for incoming text. Words up to the break point are synthesized as new text is moved into the buffer; no hierarchical structure is built beyond the lexical level. The parser was developed for use in a system that synthesizes written telecommunications by Deaf and hard of hearing people. These are texts written entirely in upper case, with little or no punctuation, and using a nonstandard variety of English (e.g. WHEN DO I WILL CALL BACK YOU). The parser performed well in a three month field trial utilizing tens of thousands of texts. Laboratory tests indicate that the parser exhibited a low error rate when compared with a human reader.

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