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Philosophical Transactions of the Royal... Mar 2018The terminal regions of eukaryotic chromosomes, composed of telomere repeat sequences and sub-telomeric sequences, represent some of the most variable and rapidly... (Review)
Review
The terminal regions of eukaryotic chromosomes, composed of telomere repeat sequences and sub-telomeric sequences, represent some of the most variable and rapidly evolving regions of the genome. The sub-telomeric regions are characterized by segmentally duplicated repetitive DNA elements, interstitial telomere repeat sequences and families of variable genes. Sub-telomeric repeat sequence families are shared among multiple chromosome ends, often rendering detailed sequence characterization difficult. These regions are composed of constitutive heterochromatin and are subjected to high levels of meiotic recombination. Dysfunction within telomere repeat arrays, either due to disruption in the chromatin structure or because of telomere shortening, can lead to chromosomal fusion and the generation of large-scale genomic rearrangements across the genome. The dynamic nature of telomeric regions, therefore, provides functionally useful variation to create genetic diversity, but also provides a mechanism for rapid genomic evolution that can lead to reproductive isolation and speciation. This article is part of the theme issue 'Understanding diversity in telomere dynamics'.This article is part of the theme issue 'Understanding diversity in telomere dynamics'.
Topics: Chromosomal Instability; Chromosomes; Evolution, Molecular; Genetic Variation; Humans; Neoplasms; Recombinational DNA Repair; Telomere; Telomere Homeostasis
PubMed: 29335376
DOI: 10.1098/rstb.2016.0437 -
Biology of Reproduction Jul 2022Meiosis is the foundation of sexual reproduction, and crossover recombination is one hallmark of meiosis. Crossovers establish the physical connections between homolog...
Meiosis is the foundation of sexual reproduction, and crossover recombination is one hallmark of meiosis. Crossovers establish the physical connections between homolog chromosomes (homologs) for their proper segregation and exchange DNA between homologs to promote genetic diversity in gametes and thus progenies. Aberrant crossover patterns, e.g., absence of the obligatory crossover, are the leading cause of infertility, miscarriage, and congenital disease. Therefore, crossover patterns have to be tightly controlled. During meiosis, loop/axis organized chromosomes provide the structural basis and regulatory machinery for crossover patterning. Accumulating evidence shows that chromosome axis length regulates the numbers and the positions of crossovers. In addition, recent studies suggest that alterations in axis length and the resultant alterations in crossover frequency may contribute to evolutionary adaptation. Here, current advances regarding these issues are reviewed, the possible mechanisms for axis length regulating crossover frequency are discussed, and important issues that need further investigations are suggested.
Topics: Chromosome Segregation; Chromosomes; Meiosis; Recombination, Genetic
PubMed: 35191959
DOI: 10.1093/biolre/ioac040 -
Molecular Biology and Evolution Jan 2022Meiotic recombination is a biological process of key importance in breeding, to generate genetic diversity and develop novel or agronomically relevant haplotypes. In...
Meiotic recombination is a biological process of key importance in breeding, to generate genetic diversity and develop novel or agronomically relevant haplotypes. In crop tomato, recombination is curtailed as manifested by linkage disequilibrium decay over a longer distance and reduced diversity compared with wild relatives. Here, we compared domesticated and wild populations of tomato and found an overall conserved recombination landscape, with local changes in effective recombination rate in specific genomic regions. We also studied the dynamics of recombination hotspots resulting from domestication and found that loss of such hotspots is associated with selective sweeps, most notably in the pericentromeric heterochromatin. We detected footprints of genetic changes and structural variants, among them associated with transposable elements, linked with hotspot divergence during domestication, likely causing fine-scale alterations to recombination patterns and resulting in linkage drag.
Topics: DNA Transposable Elements; Domestication; Solanum lycopersicum; Plant Breeding; Recombination, Genetic
PubMed: 34597400
DOI: 10.1093/molbev/msab287 -
Cold Spring Harbor Perspectives in... Oct 2015The study of homologous recombination has its historical roots in meiosis. In this context, recombination occurs as a programmed event that culminates in the formation... (Review)
Review
The study of homologous recombination has its historical roots in meiosis. In this context, recombination occurs as a programmed event that culminates in the formation of crossovers, which are essential for accurate chromosome segregation and create new combinations of parental alleles. Thus, meiotic recombination underlies both the independent assortment of parental chromosomes and genetic linkage. This review highlights the features of meiotic recombination that distinguish it from recombinational repair in somatic cells, and how the molecular processes of meiotic recombination are embedded and interdependent with the chromosome structures that characterize meiotic prophase. A more in-depth review presents our understanding of how crossover and noncrossover pathways of meiotic recombination are differentiated and regulated. The final section of this review summarizes the studies that have defined defective recombination as a leading cause of pregnancy loss and congenital disease in humans.
Topics: Chromosomes; Crossing Over, Genetic; DNA; DNA Breaks, Double-Stranded; Endonucleases; Female; Humans; Maternal Age; Meiosis; Models, Genetic; Recombination, Genetic; Reproduction
PubMed: 26511629
DOI: 10.1101/cshperspect.a016618 -
BioEssays : News and Reviews in... Apr 2019Diploid germ cells produce haploid gametes through meiosis, a unique type of cell division. Independent reassortment of parental chromosomes and their recombination... (Review)
Review
Diploid germ cells produce haploid gametes through meiosis, a unique type of cell division. Independent reassortment of parental chromosomes and their recombination leads to ample genetic variability among the gametes. Importantly, new mutations also occur during meiosis, at frequencies much higher than during the mitotic cell cycles. These meiotic mutations are associated with genetic recombination and depend on double-strand breaks (DSBs) that initiate crossing over. Indeed, sequence variation among related strains is greater around recombination hotspots than elsewhere in the genome, presumably resulting from recombination-associated mutations. Significantly, enhanced mutagenicity in meiosis may lead to faster divergence during evolution, as germ-line mutations are the ones that are transmitted to the progeny and thus have an evolutionary impact. The molecular basis for mutagenicity in meiosis may be related to the repair of meiotic DSBs by polymerases, or to the exposure of single-strand DNA to mutagenic agents during its repair.
Topics: Biological Evolution; DNA Breaks, Double-Stranded; Genetic Variation; Meiosis; Mutagenesis; Recombination, Genetic
PubMed: 30920000
DOI: 10.1002/bies.201800235 -
Biochemical Society Transactions Feb 2024Meiotic recombination, a cornerstone of eukaryotic diversity and individual genetic identity, is essential for the creation of physical linkages between homologous... (Review)
Review
Meiotic recombination, a cornerstone of eukaryotic diversity and individual genetic identity, is essential for the creation of physical linkages between homologous chromosomes, facilitating their faithful segregation during meiosis I. This process requires that germ cells generate controlled DNA lesions within their own genome that are subsequently repaired in a specialised manner. Repair of these DNA breaks involves the modulation of existing homologous recombination repair pathways to generate crossovers between homologous chromosomes. Decades of genetic and cytological studies have identified a multitude of factors that are involved in meiotic recombination. Recent work has started to provide additional mechanistic insights into how these factors interact with one another, with DNA, and provide the molecular outcomes required for a successful meiosis. Here, we provide a review of the recent developments with a focus on protein structures and protein-protein interactions.
Topics: DNA Breaks, Double-Stranded; Homologous Recombination; DNA Repair; Meiosis; Chromosomes
PubMed: 38348856
DOI: 10.1042/BST20230712 -
Philosophical Transactions of the Royal... Dec 2017One of the most striking patterns of genome structure is the tight, typically negative, association between transposable elements (TEs) and meiotic recombination rates.... (Review)
Review
One of the most striking patterns of genome structure is the tight, typically negative, association between transposable elements (TEs) and meiotic recombination rates. While this is a highly recurring feature of eukaryotic genomes, the mechanisms driving correlations between TEs and recombination remain poorly understood, and distinguishing cause versus effect is challenging. Here, we review the evidence for a relation between TEs and recombination, and discuss the underlying evolutionary forces. Evidence to date suggests that overall TE densities correlate negatively with recombination, but the strength of this correlation varies across element types, and the pattern can be reversed. Results suggest that heterogeneity in the strength of selection against ectopic recombination and gene disruption can drive TE accumulation in regions of low recombination, but there is also strong evidence that the regulation of TEs can influence local recombination rates. We hypothesize that TE insertion polymorphism may be important in driving within-species variation in recombination rates in surrounding genomic regions. Furthermore, the interaction between TEs and recombination may create positive feedback, whereby TE accumulation in non-recombining regions contributes to the spread of recombination suppression. Further investigation of the coevolution between recombination and TEs has important implications for our understanding of the evolution of recombination rates and genome structure.This article is part of the themed issue 'Evolutionary causes and consequences of recombination rate variation in sexual organisms'.
Topics: DNA Transposable Elements; Eukaryota; Evolution, Molecular; Recombination, Genetic
PubMed: 29109221
DOI: 10.1098/rstb.2016.0458 -
Yeast (Chichester, England) Mar 2019In meiosis, DNA break formation and repair are essential for the formation of crossovers between homologous chromosomes. Without crossover formation, faithful meiotic... (Review)
Review
In meiosis, DNA break formation and repair are essential for the formation of crossovers between homologous chromosomes. Without crossover formation, faithful meiotic chromosome segregation and sexual reproduction cannot occur. Crossover formation is initiated by the programmed, meiosis-specific introduction of numerous DNA double-strand breaks, after which specific repair pathways promote recombination between homologous chromosomes. Despite its crucial nature, meiotic recombination is fraud with danger: When positioned or repaired inappropriately, DNA breaks can have catastrophic consequences on genome stability of the resulting gametes. As such, DNA break formation and repair needs to be carefully controlled. Within centromeres and surrounding regions (i.e., pericentromeres), meiotic crossover recombination is repressed in organisms ranging from yeast to humans, and a failure to do so is implicated in chromosome missegregation and developmental aneuploidy. (Peri)centromere sequence identity and organization diverge considerably across eukaryotes, yet suppression of meiotic DNA break formation and repair appear universal. Here, we discuss emerging work that has used budding and fission yeast systems to study the mechanisms underlying pericentromeric suppression of DNA break formation and repair. We particularly highlight a role for the kinetochore, a universally conserved, centromere-associated structure essential for chromosome segregation, in suppressing (peri)centromeric DNA break formation and repair. We discuss the current understanding of kinetochore-associated and chromosomal factors involved in this regulation and suggest future avenues of research.
Topics: Cell Cycle Proteins; Chromosomal Proteins, Non-Histone; DNA Breaks, Double-Stranded; DNA Repair; DNA, Fungal; Kinetochores; Meiosis; Recombination, Genetic; Yeasts; Cohesins
PubMed: 30625250
DOI: 10.1002/yea.3366 -
Trends in Genetics : TIG May 2017Rates of meiotic recombination are widely variable both within and among species. However, the functional significance of this variation remains largely unknown. Is the... (Review)
Review
Rates of meiotic recombination are widely variable both within and among species. However, the functional significance of this variation remains largely unknown. Is the observed within-species variation in recombination rate adaptive? Recent work has revealed new insight into the scale and scope of population-level variation in recombination rate. These data indicate that the magnitude of within-population variation in recombination is similar among taxa. The apparent similarity of the variance in recombination rate among individuals between distantly related species suggests that the relative costs and benefits of recombination that establish the upper and lower bounds may be similar across species. Here we review the current data on intraspecific variation in recombination rate and discuss the molecular and evolutionary costs and benefits of recombination frequency. We place this variation in the context of adaptation and highlight the need for more empirical studies focused on the adaptive value of variation in recombination rate.
Topics: Animals; Evolution, Molecular; Genetic Variation; Humans; Meiosis; Recombination, Genetic
PubMed: 28359582
DOI: 10.1016/j.tig.2017.03.003 -
Trends in Genetics : TIG Jul 2018It is commonly assumed that sex chromosomes evolve recombination suppression because selection favours linkage between sex-determining and sexually antagonistic genes.... (Review)
Review
It is commonly assumed that sex chromosomes evolve recombination suppression because selection favours linkage between sex-determining and sexually antagonistic genes. However, although the role of sexual antagonism during sex chromosome evolution has attained strong support from theory, experimental and observational evidence is rare or equivocal. Here, we highlight alternative, often neglected, hypotheses for recombination suppression on sex chromosomes, which invoke meiotic drive, heterozygote advantage, and genetic drift, respectively. We contrast the hypotheses, the situations when they are likely to be of importance, and outline why it is surprisingly difficult to test them. Lastly, we discuss future research directions (including modelling, population genomics, comparative approaches, and experiments) to disentangle the different hypotheses of sex chromosome evolution.
Topics: Animals; Biological Evolution; Genetic Linkage; Recombination, Genetic; Sex Chromosomes
PubMed: 29716744
DOI: 10.1016/j.tig.2018.04.001