The Analysis of Tetrad Data

Papazian, Haig P.

doi:10.1093/genetics/37.2.175

Cited by 110 publications

(9 citation statements)

References 10 publications

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“…Non-parental ditype (two A b spores and two a B spores) results from a 4-strand DCO, and tetratype (A B, A b, a B, a b) results from a single crossover or a 3-strand DCO. Papazian (1952) developed a simple equation to calculate interference from the observed numbers of each class. Although widely used, these formulas are applicable only to datasets within certain parameters, and determining statistical significance between datasets if difficult.…”

Section: Interference In Tetradsmentioning

confidence: 99%

Meiotic Crossover Patterning

Pazhayam

Turcotte

Sekelsky

2021

Front. Cell Dev. Biol.

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Proper number and placement of meiotic crossovers is vital to chromosome segregation, with failures in normal crossover distribution often resulting in aneuploidy and infertility. Meiotic crossovers are formed via homologous repair of programmed double-strand breaks (DSBs). Although DSBs occur throughout the genome, crossover placement is intricately patterned, as observed first in early genetic studies by Muller and Sturtevant. Three types of patterning events have been identified. Interference, first described by Sturtevant in 1915, is a phenomenon in which crossovers on the same chromosome do not occur near one another. Assurance, initially identified by Owen in 1949, describes the phenomenon in which a minimum of one crossover is formed per chromosome pair. Suppression, first observed by Beadle in 1932, dictates that crossovers do not occur in regions surrounding the centromere and telomeres. The mechanisms behind crossover patterning remain largely unknown, and key players appear to act at all scales, from the DNA level to inter-chromosome interactions. There is also considerable overlap between the known players that drive each patterning phenomenon. In this review we discuss the history of studies of crossover patterning, developments in methods used in the field, and our current understanding of the interplay between patterning phenomena.

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Section: Interference In Tetradsmentioning

confidence: 99%

Meiotic Crossover Patterning

Pazhayam

Turcotte

Sekelsky

2021

Front. Cell Dev. Biol.

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“…Crossover interference was assayed using two approaches 71,72 . The coefficient of coincidence is obtained from the ratio of ‘observed’ to ‘expected’ crossovers, with ratios below 1 indicating positive crossover interference 71 .…”

Section: Resultsmentioning

confidence: 99%

Temporal and Functional Relationship between Synaptonemal Complex Morphogenesis and Recombination during Meiosis

Ahuja,

Sandhu,

Huang

et al. 2024

Preprint

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During prophase of meiosis I, programmed double strand breaks (DSBs) are processed into crossovers, a critical requirement for segregation of homologous chromosomes (homologs) and genome haploidization in sexually reproducing organisms. Crossovers form via homologous recombination in close temporospatial association with morphogenesis of the synaptonemal complex (SC), a proteinaceous structure that connects paired homologs along their length during the pachytene stage. Synapsis and recombination are a paradigm for the interplay between higher order chromosome structure and DNA metabolism, yet their temporal and functional relationship remains poorly understood. Probing linkage between these processes in budding yeast, we show that SC assembly is associated with a distinct threshold number of unstable D-loops. The transition from bona fide paranemic D-loops to plectonemic DSB single end invasions (SEIs) is completed during midpachynema, when the SC is fully assembled. Double Holliday junctions (dHJs) form at the time of desynapsis and are resolved into crossovers during diplonema. The SC central element component Zip1 shepherds recombination through three transitions, including DSB first end strand exchange and second end capture, as well as dHJ resolution. Zip1 mediates SEI formation independent of its polymerization whereas precocious Zip1 assembly interferes with double Holliday junction resolution. Together, our findings indicate that the synaptonemal complex controls recombination while assembled but also beyond its disassembly, possibly by establishing spatial constraints at recombination sites.

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“…We performed crossover interference analysis to determine if exo1Δ strains showed defects in addition to those seen in DSB resection and CO resolution. Crossover interference was measured on chromosome XV using both the Malkova and coefficient of coincidence (COC) methods ( S4 Table ; [ 60 , 61 , 79 ]). The Malkova method calculates the map distances for a genetic interval in the presence and absence of a crossover in an adjacent interval, whereas COC measures the double crossover rate compared to the expected rate in the absence of interference.…”

Section: Resultsmentioning

confidence: 99%

Exo1 protects DNA nicks from ligation to promote crossover formation during meiosis

et al. 2023

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In most sexually reproducing organisms crossing over between chromosome homologs during meiosis is essential to produce haploid gametes. Most crossovers that form in meiosis in budding yeast result from the biased resolution of double Holliday junction (dHJ) intermediates. This dHJ resolution step involves the actions of Rad2/XPG family nuclease Exo1 and the Mlh1-Mlh3 mismatch repair endonuclease. Here, we provide genetic evidence in baker’s yeast that Exo1 promotes meiotic crossing over by protecting DNA nicks from ligation. We found that structural elements in Exo1 that interact with DNA, such as those required for the bending of DNA during nick/flap recognition, are critical for its role in crossing over. Consistent with these observations, meiotic expression of the Rad2/XPG family member Rad27 partially rescued the crossover defect in exo1 null mutants, and meiotic overexpression of Cdc9 ligase reduced the crossover levels of exo1 DNA-binding mutants to levels that approached the exo1 null. In addition, our work identified a role for Exo1 in crossover interference. Together, these studies provide experimental evidence for Exo1-protected nicks being critical for the formation of meiotic crossovers and their distribution.

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The Analysis of Tetrad Data

Cited by 110 publications

References 10 publications

Meiotic Crossover Patterning

Meiotic Crossover Patterning

Temporal and Functional Relationship between Synaptonemal Complex Morphogenesis and Recombination during Meiosis

Exo1 protects DNA nicks from ligation to promote crossover formation during meiosis

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