The Origin and Behaviour of Chiasmata, II

Darlington, C. D.; Dark, S. O. S.

doi:10.1508/cytologia.3.169

Cited by 69 publications

(22 citation statements)

References 13 publications

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“…Crossover patterning also occurs between chromosomes. Darlington and Dark [24] reported that in a grasshopper species with a large range of chromosome sizes, every pair of homologous chromosomes always had at least one chiasma (the cytological manifestation of a crossover), called the obligate chiasma [25]. The occurrence of an obligate chiasma suggests that there is an active process, referred to as crossover assurance, that monitors the designation of crossovers on each chromosome.…”

Section: Resultsmentioning

confidence: 99%

“…Interference, the centromere effect, and the obligate chiasma were all described more than 80 years ago [4, 14, 24], but the mechanisms behind these phenomena remain unknown. These phenomena are entwined in the Class I crossover pathway, but it is unclear whether they are generated independently within this pathway or are merely different manifestations of a single regulatory process.…”

Section: Resultsmentioning

confidence: 99%

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Bloom Syndrome Helicase Promotes Meiotic Crossover Patterning and Homolog Disjunction

et al. 2017

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Summary In most sexually reproducing organisms, crossover formation between homologous chromosomes is necessary for proper chromosome disjunction during meiosis I. During meiotic recombination, a subset of programmed DNA double-strand breaks (DSBs) are repaired as crossovers, with the remainder becoming noncrossovers [1]. Whether a repair intermediate is designated to become a crossover is a highly-regulated decision that integrates several crossover patterning processes, both along chromosome arms (interference and the centromere effect) and between chromosomes (crossover assurance) [2]. Because the mechanisms that generate crossover patterning have remained elusive for over a century, it has been difficult to assess the relationship between crossover patterning and meiotic chromosome behavior. We show here that meiotic crossover patterning is lost in Drosophila melanogaster mutants that lack the Bloom syndrome helicase. In the absence of interference and the centromere effect, crossovers are distributed more uniformly along chromosomes. Crossovers even occur on the small chromosome 4, which normally never has meiotic crossovers [3]. Regulated distribution of crossovers between chromosome pairs is also lost, resulting in an elevated frequency of homologs that do not receive a crossover, which in turn leads to elevated nondisjunction.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Bloom Syndrome Helicase Promotes Meiotic Crossover Patterning and Homolog Disjunction

et al. 2017

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“…If there is a large size discrepancy between the different bivalents of an organism the length-chiasma frequency relation is not linear, all bivalents having at least one chiasma (Darlington and Dark, 1932). The short bivalents have a higher mean number of chiasmata per unit length than the others.…”

Section: The Hypothesis Of Competitionmentioning

confidence: 99%

Competition between bivalents during chiasma formation

Mather

1936

Proc. R. Soc. Lond. B

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It has long been known that crossing over in one section of a chromosome reduces the probability of further crossing over in other sections of that same chromosome. More recently it has been demonstrated by Haldane (1931) that the frequency distributions of chiasma formation in bivalents at the first division of meiosis also indicate that interference occurs. It has, however, been assumed that crossing over in one bivalent is independent of crossing over in other bivalents of the same nucleus. Recent work has rendered doubtful the validity of this assumption.

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“…They do not occur uniformly along and among chromosomes [1]–[3]. In most organisms, crossover rates (generally expressed in centimorgan per megabase – cM/Mb) vary between chromosomes: for example, in humans, from 0.96 cM/Mb for the long chromosome 1 to 2.11 cM/Mb for the small chromosome 22 [4].…”

Section: Introductionmentioning

confidence: 99%

Fine Scale Analysis of Crossover and Non-Crossover and Detection of Recombination Sequence Motifs in the Honeybee (Apis mellifera)

et al. 2012

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BackgroundMeiotic exchanges are non-uniformly distributed across the genome of most studied organisms. This uneven distribution suggests that recombination is initiated by specific signals and/or regulations. Some of these signals were recently identified in humans and mice. However, it is unclear whether or not sequence signals are also involved in chromosomal recombination of insects.MethodologyWe analyzed recombination frequencies in the honeybee, in which genome sequencing provided a large amount of SNPs spread over the entire set of chromosomes. As the genome sequences were obtained from a pool of haploid males, which were the progeny of a single queen, an oocyte method (study of recombination on haploid males that develop from unfertilized eggs and hence are the direct reflect of female gametes haplotypes) was developed to detect recombined pairs of SNP sites. Sequences were further compared between recombinant and non-recombinant fragments to detect recombination-specific motifs.ConclusionsRecombination events between adjacent SNP sites were detected at an average distance of 92 bp and revealed the existence of high rates of recombination events. This study also shows the presence of conversion without crossover (i. e. non-crossover) events, the number of which largely outnumbers that of crossover events. Furthermore the comparison of sequences that have undergone recombination with sequences that have not, led to the discovery of sequence motifs (CGCA, GCCGC, CCGCA), which may correspond to recombination signals.

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The Origin and Behaviour of Chiasmata, II

Cited by 69 publications

References 13 publications

Bloom Syndrome Helicase Promotes Meiotic Crossover Patterning and Homolog Disjunction

Bloom Syndrome Helicase Promotes Meiotic Crossover Patterning and Homolog Disjunction

Competition between bivalents during chiasma formation

Fine Scale Analysis of Crossover and Non-Crossover and Detection of Recombination Sequence Motifs in the Honeybee (Apis mellifera)

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