scholarly journals GENETIC RECOMBINATION AT THE BUFF SPORE COLOR LOCUS IN SORDARIA BREVICOLLIS. II. ANALYSIS OF FLANKING MARKER BEHAVIOR IN CROSSES BETWEEN BUFF MUTANTS

Genetics ◽  
1983 ◽  
Vol 103 (2) ◽  
pp. 161-178
Author(s):  
Helen Sang ◽  
Harold L K Whitehouse
Keyword(s):  
Genetic Recombination ◽  
Crossing Over ◽  
Wild Type ◽  
Equal Frequency ◽  
Proximal Site ◽  
The Cross ◽  
The Relationship ◽  
Aberrant Segregation ◽  
Distal Site ◽  
Hybrid Dna

ABSTRACT Aberrant asci containing one or more wild-type spores were selected from crosses between pairs of alleles of the buff locus in the presence of closely linked flanking markers. Data were obtained relating to the site of aberrant segregation and the position of any associated crossover giving recombination of flanking markers. Aberrant segregation at a proximal site within the buff gene may be associated with a crossover proximal to the site of aberrant segregation or, with equal frequency, with a crossover distal to the site of the second mutant present in the cross. Similarly, segregation at a distal site may be associated with a crossover distal to the site or, with lower frequency, with a crossover proximal to the site of the proximal mutant present in the cross. Crossovers between the alleles were rare. This evidence for the relationship between hybrid DNA and crossing over is discussed in terms of current models for the mechanism of recombination.

scholarly journals Aberrant segregation patterns and gene mappability in Ascobolus immersus

1982 ◽  
Vol 39 (2) ◽  
pp. 121-138 ◽  
Author(s):  
G. Leblon ◽  
V. Haedens ◽  
A. Kalogeropoulos ◽  
N. Paquette ◽  
J.-L. Rossignol
Keyword(s):  
Wild Type ◽  
Mismatch Correction ◽  
Conversion Frequency ◽  
Ascobolus Immersus ◽  
Strong Map ◽  
Postmeiotic Segregation ◽  
The Relationship ◽  
Gene Maps ◽  
Aberrant Segregation ◽  
Hybrid Dna

SummaryCrosses between various types of mutant giving specific patterns of aberrant segregation were performed in the b2 spore colour locus of Ascobolus immersus. The map of 41 mutations showing various patterns of aberrant segregation was established. The frequency of wild-type recombinants and the map additivity, map expansion and map contraction characteristics were shown to be strongly dependent upon the pattern of aberrant segregation of the mutations used. Mutations giving no postmeiotic segregation and an excess of conversion to wild type over conversion to mutant exhibit map expansion in small intervals and a strong map contraction in large intervals. Mutations giving postmeiotic segregations also exhibit map contraction in large intervals. Mutations giving no postmeiotic segregations and an excess of conversion to mutant over conversion to wild type show map additivity and thus provide a simple way for devising gene maps. The relationship between the mapping properties and the pattern of aberrant segregations is accounted for when considering parameters of gene conversion: frequency and distribution of hybrid DNA, frequency and direction of mismatch correction.

scholarly journals Systematic Mutagenesis of the Saccharomyces cerevisiae MLH1 Gene Reveals Distinct Roles for Mlh1p in Meiotic Crossing Over and in Vegetative and Meiotic Mismatch Repair

2003 ◽  
Vol 23 (3) ◽  
pp. 873-886 ◽  
Author(s):  
Juan Lucas Argueso ◽  
Amanda Wraith Kijas ◽  
Sumeet Sarin ◽  
Julie Heck ◽  
Marc Waase ◽  
...  
Keyword(s):  
Mismatch Repair ◽  
Ternary Complex ◽  
Genetic Recombination ◽  
Crossing Over ◽  
Wild Type ◽  
Dna Mismatch ◽  
Biochemical Assays ◽  
Postmeiotic Segregation ◽  
New Alleles

ABSTRACT In eukaryotic cells, DNA mismatch repair is initiated by a conserved family of MutS (Msh) and MutL (Mlh) homolog proteins. Mlh1 is unique among Mlh proteins because it is required in mismatch repair and for wild-type levels of crossing over during meiosis. In this study, 60 new alleles of MLH1 were examined for defects in vegetative and meiotic mismatch repair as well as in meiotic crossing over. Four alleles predicted to disrupt the Mlh1p ATPase activity conferred defects in all functions assayed. Three mutations, mlh1-2, -29, and -31, caused defects in mismatch repair during vegetative growth but allowed nearly wild-type levels of meiotic crossing over and spore viability. Surprisingly, these mutants did not accumulate high levels of postmeiotic segregation at the ARG4 recombination hotspot. In biochemical assays, Pms1p failed to copurify with mlh1-2, and two-hybrid studies indicated that this allele did not interact with Pms1p and Mlh3p but maintained wild-type interactions with Exo1p and Sgs1p. mlh1-29 and mlh1-31 did not alter the ability of Mlh1p-Pms1p to form a ternary complex with a mismatch substrate and Msh2p-Msh6p, suggesting that the region mutated in these alleles could be responsible for signaling events that take place after ternary complex formation. These results indicate that mismatches formed during genetic recombination are processed differently than during replication and that, compared to mismatch repair functions, the meiotic crossing-over role of MLH1 appears to be more resistant to mutagenesis, perhaps indicating a structural role for Mlh1p during crossing over.

THE RELATIONSHIP BETWEEN CHIASMATA AND CROSSING OVER IN TRITICUM AESTIVUM

Genetics ◽  
1973 ◽  
Vol 75 (2) ◽  
pp. 231-246
Author(s):  
T K Fu ◽  
E R Sears
Keyword(s):  
Chiasma Frequency ◽  
Rust Resistance ◽  
Genetic Recombination ◽  
Substantial Reduction ◽  
Leaf Rust Resistance ◽  
Crossing Over ◽  
Two Temperatures ◽  
Independent Behavior ◽  
The Relationship

ABSTRACT Telocentrics for the β arm of chromosome 4A and the long arm of 6B were used as cytological markers for the determination of chiasma frequency. In concomitant studies of recombination, terminal segments of rye and T. umbellulatum chromatin carrying Hp (Hairy peduncle) and Lr9 (Leaf-rust resistance), respectively, marked 4A and 6B. Two temperatures, 21° and 32°, were used for both the 4A and 6B experiments.—Only one chiasma was observed in each heteromorphic bivalent. Because there was a substantial reduction in pairing between diakinesis and metaphase I, all determinations of chiasma frequency were made at diakinesis. In the 21° experiments, agreement was good between genetic recombination and cytological prediction on the basis of the partial chiasmatypy hypothesis that each chiasma represents a crossover. At 32° both chiasma frequency and crossing over, but particularly the latter, were strongly reduced. The fewer crossovers than expected are explained in part by stickiness of chromosomes at the high temperature, sometimes resulting in adjacent chromosomes being wrongly scored as having a chiasma, and in part by premetaphase disjunction of some recombined bivalents and subsequent independent behavior of the two resulting univalents.—Male transmission of the 4A telocentric from the heteromorphic bivalent was unusually high: 51% at 21° and 31% at 32°.

scholarly journals Intragenic recombination pattern within the 164 locus of Ascobolus immersus in the presence of outside markers

1970 ◽  
Vol 16 (2) ◽  
pp. 185-206 ◽  
Author(s):  
Hanna Baranowska
Keyword(s):  
Intragenic Recombination ◽  
Crossing Over ◽  
Wild Type ◽  
Reciprocal Recombination ◽  
Random Samples ◽  
Ascobolus Immersus ◽  
The Cross

SUMMARYSeven ascospore colour mutants of the 164 locus of Ascobolus immersus were mapped, and their basic conversion frequencies established. Polarization of the sum of the basic conversion frequencies was observed. The recombination frequencies from the two-point crosses (in repulsion) are nonadditive. The influence of one mutant on the frequency of conversion of another in crosses in repulsion and coupling was pronounced. The frequency of crossing over between a pair of mutants was higher in the cross in repulsion than in coupling. A total of 535 asci containing a pair of wild-type spores were analysed from five crosses in repulsion. 193 6w:2d asci originated from the conversion of the proximal allele, 43 6w:2d asci from conversion of the distal allele and 277 asci exhibited reciprocal recombination. 54 6w:2d asci from one cross in coupling were analysed. These asci were classified and assigned to four classes: proximal allele conversion, distal allele conversion, reciprocal recombination and simultaneous conversion of wild type-alleles to mutants. In all classes of recombinant asci analysed the frequencies of additional exchanges in the adjacent intervals were higher than in random samples of asci. The wild-type chromatid was involved in the additional exchanges in the majority of crosses with a frequency exceeding 60%.

scholarly journals GENETIC HYBRIDIZATION AT THE UNLINKED THY AND STR LOCI OF STREPTOCOCCUS

Genetics ◽  
1975 ◽  
Vol 81 (2) ◽  
pp. 223-241
Author(s):  
Arnold W Ravin ◽  
Tapan Chakrabarti
Keyword(s):  
Relative Efficiency ◽  
Thymidylate Synthetase ◽  
Wild Type ◽  
Phenotypic Properties ◽  
Str Loci ◽  
The Cross ◽  
Number Of Classes ◽  
Donor Species ◽  
Original Donor ◽  
Hybrid Dna

ABSTRACT The sanguis and pneumoniae species of Streptococcus were used as recipients in transformations from str  + to str-r and from thy  - to thy  +. The str-r mutations in the two species had been previously shown to be allelic. Homology of the thy  - mutations in the two species was demonstrated in the similar phenotypic properties they conferred (death in the absence of thymidine, lack of thymidylate synthetase). The str and thy loci are unlinked in each species.——When the two species are transformed by both homospecific and heterospecific DNA, the efficiency is always lower in the heterospecific cross. The efficiency of heterospecific transformation is considerably lower at the thy than at the str locus. DNA was extracted from recipients that had integrated markers of heterospecific origin. When such hybrid DNA is tested on the original recipient species, the heterospecific markers are usually as efficient as homospecific markers. When tested on the original donor species, however, the hybrid DNA is usually more efficient than heterospecific DNA. This is true for both thy and str transformations.——Forty independent thy  + hybrids were obtained in the cross of sanguis thy  - recipients with pneumoniae thy  + DNA. These hybrids fall into a number of classes based upon the relative efficiency with which their extracted DNA's are able to transfer the thy  + marker into pneumoniae thy  - cells. The most efficient of these DNA's exhibits about 20% of the efficiency of homospecific pneumoniae thy  + DNA and three orders of magnitude greater efficiency than heterospecific sanguis thy  + DNA. Thus, very little of the inefficiency of heterospecific transformation of the thy locus is ascribable to a classic restriction mechanism. Rather, the wild-type thy  + loci in the two species appear to differ at multiple sites, and independent heterospecific transfers result in differential extents of integration of these sites. On this basis, the thy  + loci of the two species differ at a greater number of sites than do the respective str  + loci.

The Budding Yeast Msh4 Protein Functions in Chromosome Synapsis and the Regulation of Crossover Distribution

Genetics ◽  
2001 ◽  
Vol 158 (3) ◽  
pp. 1013-1025 ◽  
Author(s):  
Janet E Novak ◽  
Petra B Ross-Macdonald ◽  
G Shirleen Roeder
Keyword(s):  
Mismatch Repair ◽  
Budding Yeast ◽  
Null Mutation ◽  
Crossing Over ◽  
Wild Type ◽  
Crossover Interference ◽  
Meiotic Chromosomes ◽  
Chromosome Synapsis ◽  
Protein Functions ◽  
Or Gene

AbstractThe budding yeast MSH4 gene encodes a MutS homolog produced specifically in meiotic cells. Msh4 is not required for meiotic mismatch repair or gene conversion, but it is required for wild-type levels of crossing over. Here, we show that a msh4 null mutation substantially decreases crossover interference. With respect to the defect in interference and the level of crossing over, msh4 is similar to the zip1 mutant, which lacks a structural component of the synaptonemal complex (SC). Furthermore, epistasis tests indicate that msh4 and zip1 affect the same subset of meiotic crossovers. In the msh4 mutant, SC formation is delayed compared to wild type, and full synapsis is achieved in only about half of all nuclei. The simultaneous defects in synapsis and interference observed in msh4 (and also zip1 and ndj1/tam1) suggest a role for the SC in mediating interference. The Msh4 protein localizes to discrete foci on meiotic chromosomes and colocalizes with Zip2, a protein involved in the initiation of chromosome synapsis. Both Zip2 and Zip1 are required for the normal localization of Msh4 to chromosomes, raising the possibility that the zip1 and zip2 defects in crossing over are indirect, resulting from the failure to localize Msh4 properly.

scholarly journals UNEQUAL CROSSING OVER AT THE rRNA TANDON AS A SOURCE OF QUANTITATIVE GENETIC VARIATION IN DROSOPHILA

Genetics ◽  
1980 ◽  
Vol 95 (3) ◽  
pp. 727-742 ◽  
Author(s):  
R Frankham ◽  
D A Briscoe ◽  
R K Nurthen
Keyword(s):  
Genetic Variation ◽  
Selection Response ◽  
Crossing Over ◽  
Wild Type ◽  
X Chromosomes ◽  
Unequal Crossing Over ◽  
Quantitative Genetic ◽  
Y Chromosomes ◽  
Homozygous Line ◽  
Minimum Estimate

ABSTRACT Abdominal bristle selection lines (three high and three low) and controls were founded from a marked homozygous line to measure the contribution of sex-linked "mutations" to selection response. Two of the low lines exhibited a period of rapid response to selection in females, but not in males. There were corresponding changes in female variance, in heritabilities in females, in the sex ratio (a deficiency of females) and in fitness, as well as the appearance of a mutant phenotype in females of one line. All of these changes were due to bb alleles (partial deficiencies for the rRNA tandon) in the X chromosomes of these lines, while the Y chromosomes remained wild-type bb+. We argue that the bb alleles arose by unequal crossing over in the rRNA tandon.—A prediction of this hypothesis is that further changes can occur in the rRNA tandon as selection is continued. This has now been shown to occur.—Our minimum estimate of the rate of occurrence of changes at the rRNA tandon is 3 × 10-4. As this is substantially higher than conventional mutation rates, the questions of the mechanisms and rates of origin of new quantitative genetic variation require careful re-examination.

scholarly journals Plant Hormone Metabolome and Transcriptome Analysis of Dwarf and Wild-type Banana

2021 ◽  
Author(s):  
Biao Deng ◽  
Xuan Wang ◽  
Xing Long ◽  
Ren Fang ◽  
Shuangyun Zhou ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Transcriptome Analysis ◽  
Regulatory Mechanism ◽  
Feedback Regulation ◽  
Wild Type ◽  
Hormone Levels ◽  
Transporter Protein ◽  
Repressor Proteins ◽  
Differential Gene ◽  
The Relationship

AbstractGibberellin (GA), auxin (IAA) and brassinosteroid (BR) are indispensable in the process of plant growth and development. Currently, research on the regulatory mechanism of phytohormones in banana dwarfism is mainly focused on GA, and few studies are focused on IAA and BR. In this study, we measured the contents of endogenous GA, IAA and BR and compared the transcriptomes of wild-type Williams banana and its dwarf mutant across five successive growth periods. We investigated the relationship between hormones and banana dwarfism and explored differential gene expression through transcriptome analysis, thus revealing the possible metabolic regulatory mechanism. We inferred a complex regulatory network of banana dwarfing. In terms of endogenous hormone levels, GA and IAA had significant effects on banana dwarfing, while BR had little effect. The key gene in GA biosynthesis of is GA2ox, and the key genes in IAA biosynthesis are TDC and YUCCA. The differential expression of these genes might be the main factor affecting hormone levels and plant height. In terms of hormone signal transduction, DELLA and AUX/IAA repressor proteins were the core regulators of GA and IAA, respectively. They inhibited the process of signal transduction and had feedback regulation on hormone levels. Finally, the transporter protein PIN, AUX1/LAX protein family and ABCB subfamily played supplementary roles in the transport of IAA. These results provide new insights into GA and IAA regulation of banana growth and a reliable foundation for the improvement of dwarf varieties.

The Effect of Mismatch Repair and Heteroduplex Formation on Sexual Isolation in Bacillus

Genetics ◽  
1998 ◽  
Vol 148 (1) ◽  
pp. 13-18 ◽  
Author(s):  
Jacek Majewski ◽  
Frederick M Cohan
Keyword(s):  
Mismatch Repair ◽  
Wild Type Strain ◽  
Resistance Mechanism ◽  
Sequence Divergence ◽  
Sexual Isolation ◽  
Wild Type ◽  
Exponential Relationship ◽  
Dna Strands ◽  
The Relationship ◽  
Heteroduplex Formation

AbstractIn Bacillus transformation, sexual isolation is known to be an exponential function of the sequence divergence between donor and recipient. Here, we have investigated the mechanism under which sequence divergence results in sexual isolation. We tested the effect of mismatch repair by comparing a wild-type strain and an isogenic mismatch-repair mutant for the relationship between sexual isolation and sequence divergence. Mismatch repair was shown to contribute to sexual isolation but was responsible for only a small fraction of the sexual isolation observed. Another possible mechanism of sexual isolation is that more divergent recipient and donor DNA strands have greater difficulty forming a heteroduplex because a region of perfect identity between donor and recipient is required for initiation of the heteroduplex. A mathematical model showed that this heteroduplex-resistance mechanism yields an exponential relationship between sexual isolation and sequence divergence. Moreover, this model yields an estimate of the size of the region of perfect identity that is comparable to independent estimates for Escherichia coli. For these reasons, and because all other mechanisms of sexual isolation may be ruled out, we conclude that resistance to heteroduplex formation is predominantly responsible for the exponential relationship between sexual isolation and sequence divergence in Bacillus transformation.

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