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Journal of Microbiology (Seoul, Korea) Apr 2019During meiosis, crossing over allows for the exchange of genes between homologous chromosomes, enabling their segregation and leading to genetic variation in the... (Review)
Review
During meiosis, crossing over allows for the exchange of genes between homologous chromosomes, enabling their segregation and leading to genetic variation in the resulting gametes. Spo11, a topoisomerase-like protein expressed in eukaryotes, and diverse accessory factors induce programmed double-strand breaks (DSBs) to initiate meiotic recombination during the early phase of meiosis after DNA replication. DSBs are further repaired via meiosis-specific homologous recombination. Studies on budding yeast have provided insights into meiosis and genetic recombination and have improved our understanding of higher eukaryotic systems. Cohesin, a chromosome-associated multiprotein complex, mediates sister chromatid cohesion (SCC), and is conserved from yeast to humans. Diverse cohesin subunits in budding yeast have been identified in DNA metabolic pathways, such as DNA replication, chromosome segregation, recombination, DNA repair, and gene regulation. During cell cycle, SCC is established by multiple cohesin subunits, which physically bind sister chromatids together and modulate proteins that involve in the capturing and separation of sister chromatids. Cohesin components include at least four core subunits that establish and maintain SCC: two structural maintenance chromosome subunits (Smc1 and Smc3), an α-kleisin subunit (Mcd1/Scc1 during mitosis and Rec8 during meiosis), and Scc3/Irr1 (SA1 and SA2). In addition, the cohesin-associated factors Pds5 and Rad61 regulate structural modifications and cell cyclespecific dynamics of chromatin to ensure accurate chromosome segregation. In this review, we discuss SCC and the recombination pathway, as well as the relationship between the two processes in budding yeast, and we suggest a possible conserved mechanism for meiotic chromosome dynamics from yeast to humans.
Topics: Chromosomes, Fungal; Fungal Proteins; Meiosis; Recombination, Genetic; Saccharomycetales
PubMed: 30671743
DOI: 10.1007/s12275-019-8541-9 -
The New Phytologist Feb 20171022 I. 1022 II. 1023 III. 1023 IV. 1025 V. 1026 1027 References 1027 SUMMARY: Meiosis is fundamental to sexual reproduction and creates genetic variation in progeny.... (Review)
Review
1022 I. 1022 II. 1023 III. 1023 IV. 1025 V. 1026 1027 References 1027 SUMMARY: Meiosis is fundamental to sexual reproduction and creates genetic variation in progeny. During meiosis paired homologous chromosomes undergo recombination, which can result in reciprocal crossovers. This process can recombine independently arising mutations onto the same chromosome. Recombination locations are highly variable between meioses, although total crossover numbers are tightly regulated. In addition to the effect of meiosis on genetic variation, sequence polymorphisms between homologous chromosomes can feedback onto the recombination pathways. Here we review the major crossover pathways in plants and some of the known homeostatic mechanisms that act during meiotic recombination. We then examine how sequence polymorphisms between homologous chromosomes, that is, heterozygosity, can influence meiotic recombination pathways in cis and trans. Finally, we provide a brief perspective on the relevance of these interconnections for natural selection and adaptation in plants.
Topics: Base Sequence; Feedback; Genome, Plant; Meiosis; Polymorphism, Genetic; Recombination, Genetic
PubMed: 27861941
DOI: 10.1111/nph.14265 -
Prenatal Diagnosis Apr 2021The physical exchange of DNA between homologs, crossing-over, is essential to orchestrate the unique, reductional first meiotic division (MI). In females, the events of...
The physical exchange of DNA between homologs, crossing-over, is essential to orchestrate the unique, reductional first meiotic division (MI). In females, the events of meiotic recombination that serve to tether homologs and facilitate their disjunction at MI occur during fetal development, preceding the MI division by several decades in our species. Data from studies in humans and mice demonstrate that placement of recombination sites during fetal development influences the likelihood of an MI nondisjunction event that results in the production of an aneuploid egg. Here we briefly summarize what we know about the relationship between aneuploidy and meiotic recombination and important considerations for the future of human assisted reproduction.
Topics: Aneuploidy; Crossing Over, Genetic; Humans; Meiosis
PubMed: 33484483
DOI: 10.1002/pd.5910 -
Philosophical Transactions of the Royal... Dec 2017For over a century, scientists have known that meiotic recombination rates can vary considerably among individuals, and that environmental conditions can modify... (Review)
Review
For over a century, scientists have known that meiotic recombination rates can vary considerably among individuals, and that environmental conditions can modify recombination rates relative to the background. A variety of external and intrinsic factors such as temperature, age, sex and starvation can elicit 'plastic' responses in recombination rate. The influence of recombination rate plasticity on genetic diversity of the next generation has interesting and important implications for how populations evolve. Further, many questions remain regarding the mechanisms and molecular processes that contribute to recombination rate plasticity. Here, we review 100 years of experimental work on recombination rate plasticity conducted in We categorize this work into four major classes of experimental designs, which we describe via classic studies in Based on these studies, we highlight molecular mechanisms that are supported by experimental results and relate these findings to studies in other systems. We synthesize lessons learned from this model system into experimental guidelines for using recent advances in genotyping technologies, to study recombination rate plasticity in non-model organisms. Specifically, we recommend (1) using fine-scale genome-wide markers, (2) collecting time-course data, (3) including crossover distribution measurements, and (4) using mixed effects models to analyse results. To illustrate this approach, we present an application adhering to these guidelines from empirical work we conducted in This article is part of the themed issue 'Evolutionary causes and consequences of recombination rate variation in sexual organisms'.
Topics: Animals; Drosophila melanogaster; Genetic Variation; Genotyping Techniques; Models, Genetic; Recombination, Genetic
PubMed: 29109222
DOI: 10.1098/rstb.2016.0459 -
Annual Review of Genetics Nov 2016Comparisons among a variety of eukaryotes have revealed considerable variability in the structures and processes involved in their meiosis. Nevertheless, conventional... (Review)
Review
Comparisons among a variety of eukaryotes have revealed considerable variability in the structures and processes involved in their meiosis. Nevertheless, conventional forms of meiosis occur in all major groups of eukaryotes, including early-branching protists. This finding confirms that meiosis originated in the common ancestor of all eukaryotes and suggests that primordial meiosis may have had many characteristics in common with conventional extant meiosis. However, it is possible that the synaptonemal complex and the delicate crossover control related to its presence were later acquisitions. Later still, modifications to meiotic processes occurred within different groups of eukaryotes. Better knowledge on the spectrum of derived and uncommon forms of meiosis will improve our understanding of many still mysterious aspects of the meiotic process and help to explain the evolutionary basis of functional adaptations to the meiotic program.
Topics: Alveolata; Amoebozoa; Animals; Chromosome Pairing; Eukaryota; Fungi; Meiosis; Prophase; Recombination, Genetic; Stramenopiles; Synaptonemal Complex
PubMed: 27686280
DOI: 10.1146/annurev-genet-120215-035100 -
Cold Spring Harbor Perspectives in... Oct 2014Meiotic recombination involves the formation and repair of programmed DNA double-strand breaks (DSBs) catalyzed by the conserved Spo11 protein. This review summarizes... (Review)
Review
Meiotic recombination involves the formation and repair of programmed DNA double-strand breaks (DSBs) catalyzed by the conserved Spo11 protein. This review summarizes recent studies pertaining to the formation of meiotic DSBs, including the mechanism of DNA cleavage by Spo11, proteins required for break formation, and mechanisms that control the location, timing, and number of DSBs. Where appropriate, findings in different organisms are discussed to highlight evolutionary conservation or divergence.
Topics: Animals; Biological Evolution; Cell Cycle Proteins; DNA Breaks, Double-Stranded; DNA Repair; Endodeoxyribonucleases; Humans; Meiosis; Protein Interaction Maps; Recombination, Genetic; Signal Transduction; Species Specificity
PubMed: 25324213
DOI: 10.1101/cshperspect.a016634 -
Proceedings. Biological Sciences Sep 2016Meiosis is an ancestral, highly conserved process in eukaryotic life cycles, and for all eukaryotes the shared component of sexual reproduction. The benefits and... (Review)
Review
Meiosis is an ancestral, highly conserved process in eukaryotic life cycles, and for all eukaryotes the shared component of sexual reproduction. The benefits and functions of meiosis, however, are still under discussion, especially considering the costs of meiotic sex. To get a novel view on this old problem, we filter out the most conserved elements of meiosis itself by reviewing the various modifications and alterations of modes of reproduction. Our rationale is that the indispensable steps of meiosis for viability of offspring would be maintained by strong selection, while dispensable steps would be variable. We review evolutionary origin and processes in normal meiosis, restitutional meiosis, polyploidization and the alterations of meiosis in forms of uniparental reproduction (apomixis, apomictic parthenogenesis, automixis, selfing) with a focus on plants and animals. This overview suggests that homologue pairing, double-strand break formation and homologous recombinational repair at prophase I are the least dispensable elements, and they are more likely optimized for repair of oxidative DNA damage rather than for recombination. Segregation, ploidy reduction and also a biparental genome contribution can be skipped for many generations. The evidence supports the theory that the primary function of meiosis is DNA restoration rather than recombination.
Topics: Animals; Biological Evolution; Eukaryota; Meiosis; Plants; Recombination, Genetic; Reproduction
PubMed: 27605505
DOI: 10.1098/rspb.2016.1221 -
DNA Repair Apr 2016Recombination hotspots are the regions within the genome where the rate, and the frequency of recombination are optimum with a size varying from 1 to 2kb. The... (Review)
Review
Recombination hotspots are the regions within the genome where the rate, and the frequency of recombination are optimum with a size varying from 1 to 2kb. The recombination event is mediated by the double-stranded break formation, guided by the combined enzymatic action of DNA topoisomerase and Spo 11 endonuclease. These regions are distributed non-uniformly throughout the human genome and cause distortions in the genetic map. Numerous lines of evidence suggest that the number of hotspots known in humans has increased manifold in recent years. A few facts about the hotspot evolutions were also put forward, indicating the differences in the hotspot position between chimpanzees and humans. In mice, recombination hot spots were found to be clustered within the major histocompatibility complex (MHC) region. Several models, that help explain meiotic recombination has been proposed. Moreover, scientists also developed some computational tools to locate the hotspot position and estimate their recombination rate in humans is of great interest to population and medical geneticists. Here we reviewed the molecular mechanisms, models and in silico prediction techniques of hot spot residues.
Topics: Animals; Computer Simulation; DNA End-Joining Repair; Humans; Models, Genetic; Recombination, Genetic; Recombinational DNA Repair
PubMed: 26991854
DOI: 10.1016/j.dnarep.2016.02.005 -
Cell Nov 2021Numerous DNA double-strand breaks (DSBs) arise during meiosis to initiate homologous recombination. These DSBs are usually repaired faithfully, but here, we uncover a...
Numerous DNA double-strand breaks (DSBs) arise during meiosis to initiate homologous recombination. These DSBs are usually repaired faithfully, but here, we uncover a distinct type of mutational event in which deletions form via joining of ends from two closely spaced DSBs (double cuts) within a single hotspot or at adjacent hotspots on the same or different chromatids. Deletions occur in normal meiosis but are much more frequent when DSB formation is dysregulated in the absence of the ATM kinase. Events between chromosome homologs point to multi-chromatid damage and aborted gap repair. Some deletions contain DNA from other hotspots, indicating that double cutting at distant sites creates substrates for insertional mutagenesis. End joining at double cuts can also yield tandem duplications or extrachromosomal circles. Our findings highlight the importance of DSB regulation and reveal a previously hidden potential for meiotic mutagenesis that is likely to affect human health and genome evolution.
Topics: Animals; Ataxia Telangiectasia Mutated Proteins; Base Sequence; Chromatids; Chromosomes, Mammalian; Crosses, Genetic; DNA Breaks, Double-Stranded; DNA, Circular; Female; Gene Deletion; Gene Duplication; Genome; Germ Cells; Haplotypes; Homologous Recombination; Male; Mice, Inbred C57BL; Mice, Inbred DBA; Mutagenesis, Insertional; Mutation; Recombination, Genetic; Mice
PubMed: 34793701
DOI: 10.1016/j.cell.2021.10.025 -
Genes Sep 2021Plant cytogenetic studies have provided essential knowledge on chromosome behavior during meiosis, contributing to our understanding of this complex process. In this... (Review)
Review
Plant cytogenetic studies have provided essential knowledge on chromosome behavior during meiosis, contributing to our understanding of this complex process. In this review, we describe in detail the meiotic process in auto- and allopolyploids from the onset of prophase I through pairing, recombination, and bivalent formation, highlighting recent findings on the genetic control and mode of action of specific proteins that lead to diploid-like meiosis behavior in polyploid species. During the meiosis of newly formed polyploids, related chromosomes (homologous in autopolyploids; homologous and homoeologous in allopolyploids) can combine in complex structures called multivalents. These structures occur when multiple chromosomes simultaneously pair, synapse, and recombine. We discuss the effectiveness of crossover frequency in preventing multivalent formation and favoring regular meiosis. Homoeologous recombination in particular can generate new gene (locus) combinations and phenotypes, but it may destabilize the karyotype and lead to aberrant meiotic behavior, reducing fertility. In crop species, understanding the factors that control pairing and recombination has the potential to provide plant breeders with resources to make fuller use of available chromosome variations in number and structure. We focused on wheat and oilseed rape, since there is an abundance of elucidating studies on this subject, including the molecular characterization of the (wheat) and (oilseed rape) loci, which are known to play a crucial role in regulating meiosis. Finally, we exploited the consequences of chromosome pairing and recombination for genetic map construction in polyploids, highlighting two case studies of complex genomes: (i) modern sugarcane, which has a man-made genome harboring two subgenomes with some recombinant chromosomes; and (ii) hexaploid sweet potato, a naturally occurring polyploid. The recent inclusion of allelic dosage information has improved linkage estimation in polyploids, allowing multilocus genetic maps to be constructed.
Topics: Brassica napus; Chromosomes, Plant; Crossing Over, Genetic; Meiosis; Plant Breeding; Polyploidy; Triticum
PubMed: 34680912
DOI: 10.3390/genes12101517