Estimation of Genetic Recombination Frequency with the Help of Logarithm Of Odds (LOD) Method

ABSTRACT Sexual crosses between strains of Phycomyces blakesleeanus, involving three auxotrophic and one color marker and yielding a high proportion of zygospore germination, are described. Samples of 20-40 germ spores from 311 individual fertile germ sporangia originating from five two-factor and three three-factor crosses were characterized. The results show: (1) absence of any contribution of apogamic nuclei to the progeny, (2) confirmation of Burgeff's conjecture that the germ spores of any germ sporangium in most cases derive from one meiosis. In a cross involving two allelic markers the analysis of 175 pooled germ sporangia suggests an intragenic recombination frequency of 0.6%. All other factor combinations tested are unlinked. The bulk of the germ spores are homokaryotic. However, a small portion (4%) are heterokaryotic with respect to mating type.

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Genetic Recombination in Coprinus

Journal of Cell Science ◽

10.1242/jcs.6.3.669 ◽

1970 ◽

Vol 6 (3) ◽

pp. 669-678

Author(s):

B. C. LU

Keyword(s):

Fruiting Body ◽

Temperature Effects ◽

Cold Shock ◽

Genetic Recombination ◽

Recombination Frequency ◽

Temperature Treatment ◽

Sensitive Period ◽

Crossing Over ◽

Synaptinemal Complex ◽

Before And After

The frequency of genetic recombination in Coprinus lagopus may be modified by heat and cold shock. By removal of samples from a fruiting body before and after temperature treatment, it is possible to study the ultrastructure of chromosomes at the time recombination frequency (between den+ x +me-1) can be modified. The sensitive period for temperature effects and, therefore, probably the time of crossing over, commences with the formation of the synaptinemal complex (S.C.) and ends with its disappearance, i.e. during the entire existence of the S.C. It is concluded that recombination is an event subsequent to the formation of the S.C. and is independent of the process of its formation. It is suggested that the event takes place at the synaptic centre.

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RECOMBINATION IN THE VICINITY OF INSERTIONS OF TRANSPOSON Tn5 IN MYXOCOCCUS XANTHUS

Genetics ◽

10.1093/genetics/105.2.281 ◽

1983 ◽

Vol 105 (2) ◽

pp. 281-291

Author(s):

Erica Sodergren ◽

Yvonne Cheng ◽

Leon Avery ◽

Dale Kaiser

Keyword(s):

Genetic Recombination ◽

Recombination Frequency ◽

Myxococcus Xanthus ◽

Physical Distance ◽

The Other ◽

Restriction Map ◽

Transposon Tn5 ◽

Good Correspondence ◽

Reciprocal Crosses ◽

Two Measures

ABSTRACT To test genetic recombination in the vicinity of insertions of the transposon Tn5, crosses were performed by transduction between M. xanthus strains carrying different insertions of Tn5. One member of each pair carried resistance to kanamycin (Tn5-Km); the other carried resistance to tetracycline (Tn5-Tc). The distance between each pair of Tn5 insertions was also measured by restriction mapping. The physical distance corresponding to each recombination frequency was calculated from the transductional linkage and compared with distance on the restriction map. A good correspondence between the two measures of distance was obtained for a pair of Tn5 insertions near the cglB locus and for another pair near the mgl locus. Correspondence between the two measurements of distance, the observed allelic behavior of Tn5-Km and Tn5-Tc at the same locus and the finding of the same frequencies of recombinants in reciprocal crosses implied that recombination in the vicinity of Tn5 was normal.

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Genome Duplication Increases Meiotic Recombination Frequency: A Saccharomyces cerevisiae Model

Molecular Biology and Evolution ◽

10.1093/molbev/msaa219 ◽

2020 ◽

Author(s):

Ou Fang ◽

Lin Wang ◽

Yuxin Zhang ◽

Jixuan Yang ◽

Qin Tao ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Meiotic Recombination ◽

Genome Stability ◽

Genome Duplication ◽

Genetic Recombination ◽

Recombination Frequency ◽

Abiotic Factors ◽

Strand Break ◽

Homologous Chromosomes ◽

Almost All

Abstract Genetic recombination characterized by reciprocal exchange of genes on paired homologous chromosomes is the most prominent event in meiosis of almost all sexually reproductive organisms. It contributes to genome stability by ensuring the balanced segregation of paired homologs in meiosis, and it is also the major driving factor in generating genetic variation for natural and artificial selection. Meiotic recombination is subjected to the control of a highly stringent and complex regulating process and meiotic recombination frequency (MRF) may be affected by biological and abiotic factors such as sex, gene density, nucleotide content, and chemical/temperature treatments, having motivated tremendous researches for artificially manipulating MRF. Whether genome polyploidization would lead to a significant change in MRF has attracted both historical and recent research interests; however, tackling this fundamental question is methodologically challenging due to the lack of appropriate methods for tetrasomic genetic analysis, thus has led to controversial conclusions in the literature. This article presents a comprehensive and rigorous survey of genome duplication-mediated change in MRF using Saccharomyces cerevisiae as a eukaryotic model. It demonstrates that genome duplication can lead to consistently significant increase in MRF and rate of crossovers across all 16 chromosomes of S. cerevisiae, including both cold and hot spots of MRF. This ploidy-driven change in MRF is associated with weakened recombination interference, enhanced double-strand break density, and loosened chromatin histone occupation. The study illuminates a significant evolutionary feature of genome duplication and opens an opportunity to accelerate response to artificial and natural selection through polyploidization.

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Involvement of Coprinus endonuclease in preparing substrate for in vitro recombination

Genome ◽

10.1139/g90-016 ◽

1990 ◽

Vol 33 (1) ◽

pp. 101-108 ◽

Cited By ~ 3

Author(s):

G. P. Montgomery ◽

B. C. Lu

Keyword(s):

Plasmid Dna ◽

Genetic Recombination ◽

Recombination Frequency ◽

Fold Increase ◽

Electrophoretic Analysis ◽

Site Specific ◽

Circular Plasmid ◽

In Vitro Recombination ◽

Recombination Assay

A functional recombination assay involving the tetracycline mutant plasmids, pUW1 and pUW4, was used to assess (i) the nature of the DNA substrates needed and (ii) the involvement of Coprinus endonuclease in preparing substrate, for the RecA-directed recombination process. A gapped circular plasmid and a linear or a nicked circular plasmid are efficient substrate combinations in this system to achieve a 160-fold increase in the in vitro recombination frequency over the control levels. The Coprinus endonuclease obtained from early meiotic prophase can produce such substrates. The recombination frequency obtained with the combination of gapped pUW1 plasmids initially relaxed by the Coprinus endonuclease and linear pUW4 plasmids produced by the site-specific BamHI digest is 10-fold lower than that obtained when both substrates are digested by BamHI. The results suggest that the Coprinus endonuclease creates random nicks on plasmid DNA. Glyoxal gel electrophoretic analysis was used to confirm this random nicking activity of Coprinus endonuclease.Key words: Coprinus, genetic recombination, endonuclease, recA.

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Allopolyploidization Enhances Genetic Recombination of the Ancestral Diploid Genome in the Evolution of Wheat

10.21203/rs.3.rs-80690/v1 ◽

2020 ◽

Author(s):

Hongshen Wan ◽

Jun Li ◽

Shengwei Ma ◽

Fan Yang ◽

Liang Chai ◽

...

Keyword(s):

Hexaploid Wheat ◽

Genetic Recombination ◽

Recombination Frequency ◽

Aegilops Tauschii ◽

Synthetic Hexaploid Wheat ◽

Evolutionary Potential ◽

D Genome ◽

Diploid Genome ◽

Synthetic Hexaploid ◽

The Impact

Abstract Background: Genetic recombination produces different allelic combinations potentially, providing new variations to the selection pools for domestication. Allopolyploidization increases evolutionary potential of the hexaploid common wheat by taking its advantages of heterosis and gene redundancy. May there be any relationship between allopolyploidization and genetic recombination? To study the impact of allopolyploidization on genetic recombination in different ancestral genomes of wheat, we generated synthetic hexaploid wheat by crossed tetraploid Triticum turgidum with diploid Aegilops tauschii to simulate its evolutionary hexaploidization process. Results: Using Wheat Breeder’s Genotyping Array, the genotypes of F2 individuals were investigated in both tetraploid (A1A1B1B1 x A2A2B2B2) and their synthetic hexaploid wheat derived populations (A1A1B1B1DD x A2A2B2B2DD). And the genotypes of the diploid population (D1D1 x D2D2) and their synthetic hexaploid wheat derived population (AABBD1D1 x AABBD2D2) were obtained with DArT-Seq™ technology. Based on genotypes of F2 populations, the genetic recombination frequency of homologous chromosome were consequently calculated in ancestral tetraploid AABB (4x), diploid DD (2x) and their synthetic hexaploid AABBDD (6x) plants, respectively. The recombination frequency of the ancestral diploid genome DD from Aegilops tauschii was found enhanced significantly more than 2 folds after their hexaploidization, while no significant changes was found in their ancestral tetraploid genome AABB via hexaploidization.Conclusions: Allopolyploidization enhancing genetic recombination of the ancestral diploid genome is found to increase the evolutionary potential of wheat, which is beneficial for wheat to conquer their narrow origination of D genome, quickly spread and make it a major crop of the world.

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GENETIC RECOMBINATION IN COPRINUS. IV. A KINETIC STUDY OF THE TEMPERATURE EFFECT ON RECOMBINATION FREQUENCY

Genetics ◽

10.1093/genetics/78.2.661 ◽

1974 ◽

Vol 78 (2) ◽

pp. 661-677

Author(s):

B C Lu

Keyword(s):

Heat Treatment ◽

Genetic Recombination ◽

Recombination Frequency ◽

Cold Treatment ◽

Continuous Light ◽

S Phase ◽

Critical Stage ◽

Maximum Increase ◽

Treatment Conditions ◽

Rate Of Increase

ABSTRACT At the restrictive conditions (35° under continuous light) Coprinus lagopus is unable to initiate premeiotic S phase which takes place normally within 8-10 h of karyogamy. A shift-up to the restrictive conditions causes an arrest of the basidiocarps at this critical stage. A prolonged arrest causes a reversal to mitosis (Lu 1974b). Incubation of basidiocarps at the restrictive conditions before this critical stage causes no increase in recombination frequency (R.F.) in the loci studied. An arrest of 4 h at the critical stage still causes no R.F. increase, but 12-13 h and 18-19 h arrests cause increases of 50% and 90% over the controls, respectively. Thus R.F. can be increased even before the cells are fully committed to meiosis.—A 3-h heat treatment at the beginning of S phase (or 8 h before karyogamy) also causes some (30%) increase in R.F. while the same treatment at late S phase (or 3 h before karyogamy) causes a substantial (164%) increase in R.F. over the controls. A 3-h heat treatment before S phase causes no increase in R.F.—Pachytene is also responsive to temperature treatments (Lu 1969). The maximum R.f. increase is 100% by heat and 220% by cold treatment. The shortest time that can cause the maximum increase in recombination by high temperature is 3 h and that by cold treatment is 7 h. These durations are correlated with the length of the pachytene stage under the treatment conditions. The kinetic data show that the increase in R.F. caused by high and low temperatures follows two-hit kinetics and their rate of increase is almost identical. The higher increase in R.F. by low temperature can be attributed to the increased duration of pachytene and therefore R.F. is a function of time. The longer the homologous chromosomes are held together, the higher the recombination frequency.

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HOMOLOGOUS RECOMBINATION BETWEEN EPISOMAL PLASMIDS AND CHROMOSOMES IN YEAST

Genetics ◽

10.1093/genetics/105.4.843 ◽

1983 ◽

Vol 105 (4) ◽

pp. 843-856

Author(s):

S Carl Falco ◽

Mark Rose ◽

David Botstein

Keyword(s):

Fine Structure ◽

Homologous Recombination ◽

Genetic Recombination ◽

Recombination Frequency ◽

Mitotic Recombination ◽

Base Pairs ◽

The Third ◽

Chromosome Recombination ◽

Gene Conversions ◽

Double Crossovers

ABSTRACT We have observed genetic recombination between ura3 - mutations (among them extensive deletions) carried on "episomal" (i.e., 2μ DNA-containing) plasmids and other ura3 - alleles present at the normal chromosomal URA3 locus. The recombination frequency found was comparable to the level observed for classical mitotic recombination but was relatively insensitive to sunlamp radiation, which strongly stimulates mitotic recombination. Three equally frequent classes could be distinguished among the recombinants. Two of these are the apparent result of gene conversions (or double crossovers) which leave the URA3 + allele on the chromosome (class I) or on the plasmid (class II). The third class is apparently due to a single crossover that results in the integration of the plasmid into a chromosome. Plasmid-chromosome recombination can be useful in fine structure genetic mapping, since recombination between a chromosomal point mutation and a plasmid-borne deletion mutation only 25 base pairs distant was easily detected.

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GENETIC CONTROL OF MEIOSIS IN RICE, ORYZA SATIVA L. III. EFFECT OF DS GENES ON GENETIC RECOMBINATION

Genetics ◽

10.1093/genetics/108.3.697 ◽

1984 ◽

Vol 108 (3) ◽

pp. 697-706

Author(s):

Kunio Kitada ◽

Takeshi Omura

Keyword(s):

Oryza Sativa ◽

Chiasma Frequency ◽

Genetic Recombination ◽

Recombination Frequency ◽

Oryza Sativa L ◽

The Other ◽

Crossing Over ◽

Homozygous Condition ◽

Synaptonemal Complexes ◽

The Mean

ABSTRACT The recombination frequency as influenced by five independent recessive ds genes was measured on three segments of different chromosomes of rice, Oryza sativa L. Each ds gene in the homozygous condition resulted in an almost equally reduced recombination frequency in the three segments. When the mean reduction in recombination frequency was related to the reduction of chiasma frequency, the five ds genes were divided into two types: in one type the reduction of chiasma frequency almost corresponded to the mean reduction of recombination frequency, and in the other the chiasma frequency was greatly reduced in comparison with the mean reduction of recombination frequency. Three of the five ds genes were found to belong to the former group. In both types, normal synaptonemal complexes were observed in pachytene cells homozygous for ds genes. This finding suggests that ds genes do not affect the formation of synaptonemal complexes which are regarded as the prerequisite structure for crossing over.

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Concurrent Disruption of Genetic Interference and Increase of Genetic Recombination Frequency in Hybrid Rice Using CRISPR/Cas9

Frontiers in Plant Science ◽

10.3389/fpls.2021.757152 ◽

2021 ◽

Vol 12 ◽

Author(s):

Chaolei Liu ◽

Yiwei Cao ◽

Yufeng Hua ◽

Guijie Du ◽

Qing Liu ◽

...

Keyword(s):

Genetic Diversity ◽

Hybrid Rice ◽

Genetic Recombination ◽

Recombination Frequency ◽

Rice Variety ◽

Female Fertility ◽

Central Component ◽

Linkage Drag ◽

Genetic Interference ◽

Null Mutants

Manipulation of the distribution and frequency of meiotic recombination events to increase genetic diversity and disrupting genetic interference are long-standing goals in crop breeding. However, attenuation of genetic interference is usually accompanied by a reduction in recombination frequency and subsequent loss of plant fertility. In the present study, we generated null mutants of the ZEP1 gene, which encodes the central component of the meiotic synaptonemal complex (SC), in a hybrid rice using CRISPR/Cas9. The null mutants exhibited absolute male sterility but maintained nearly unaffected female fertility. By pollinating the zep1 null mutants with pollen from indica rice variety 93-11, we successfully conducted genetic analysis and found that genetic recombination frequency was greatly increased and genetic interference was completely eliminated in the absence of ZEP1. The findings provided direct evidence to support the controversial hypothesis that SC is involved in mediating interference. Additionally, the remained female fertility of the null mutants makes it possible to break linkage drag. Our study provides a potential approach to increase genetic diversity and fully eliminate genetic interference in rice breeding.

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