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Although sexual antagonism may have played a role in forming some sex chromosome systems, there appears to be little empirical or theoretical justification in assuming that it is the driving force in all cases of sex chromosome evolution. In many species, sex chromosomes have diverged in size and shape through the accumulation of mutations in regions of suppressed recombination. It is commonly assumed...
The organisation of mammalian mitochondrial DNA (mtDNA) is more complex than usually assumed. Despite often being depicted as a simple circle, the topology of mtDNA can vary from supercoiled monomeric circles over catenanes and oligomers to complex multimeric networks. Replication of mtDNA is also not clear cut. Two different mechanisms of replication have been found in cultured cells and in most...
We suggest that supergenes, groups of co‐inherited loci, may be involved in a range of intriguing genetic and evolutionary phenomena in insect societies, and may play broad roles in the evolution of cooperation and conflict. Supergenes are central in the evolution of an array of traits including self‐incompatibility, mimicry, and sex chromosomes. Recently, researchers identified a large supergene,...
All species continuously evolve to adapt to changing environments. The genetic variation that fosters such adaptation is caused by a plethora of mechanisms, including meiotic recombination that generates novel allelic combinations in the progeny of two parental lineages. However, a considerable number of eukaryotic species, including many fungi, do not have an apparent sexual cycle and are consequently...
Replication of the main chromosome in the halophilic archaeon Haloferax volcanii was recently reported to continue despite deletion of all active replication origins. Equally surprising, the deletion strain grew faster than the parent strain. It was proposed that origin‐less H. volcanii duplicate their chromosomes via recombination‐dependent replication. Here, we recall our present knowledge of this...
Recombination maps of ancestral species can be constructed from comparative analyses of genomes from closely related species, exemplified by a recently published map of the human‐chimpanzee ancestor. Such maps resolve differences in recombination rate between species into changes along individual branches in the speciation tree, and allow identification of associated changes in the genomic sequences...
Replication protein A (RPA), the major single‐stranded DNA‐binding protein in eukaryotic cells, is required for processing of single‐stranded DNA (ssDNA) intermediates found in replication, repair, and recombination. Recent studies have shown that RPA binding to ssDNA is highly dynamic and that more than high‐affinity binding is needed for function. Analysis of DNA binding mutants identified forms...
Our understanding of genomic reorganization, the mechanics of genomic transmission to offspring during germ line formation, and how these structural changes contribute to the speciation process, and genetic disease is far from complete. Earlier attempts to understand the mechanism(s) and constraints that govern genome remodeling suffered from being too narrowly focused, and failed to provide a unified...
The evolution of sex in eukaryotes represents a paradox, given the “twofold” fitness cost it incurs. We hypothesize that the mutational dynamics of the mitochondrial genome would have favored the evolution of sexual reproduction. Mitochondrial DNA (mtDNA) exhibits a high‐mutation rate across most eukaryote taxa, and several lines of evidence suggest that this high rate is an ancestral character....
The origin and evolutionary dynamics of the spatial heterogeneity in genomic base composition have been debated since its discovery in the 1970s. With the recent availability of numerous genome sequences from a wide range of species it has been possible to address this question from a comparative perspective, and similarities and differences in base composition between groups of organisms are becoming...
Mammalian mitochondrial DNA (mtDNA) replication and repair have been studied intensively for the last 50 years. Although recently advances in elucidating the molecular mechanisms of mtDNA maintenance and the proteins involved in these have been made, there are disturbing gaps between the existing theoretical models and experimental observations. Conflicting data and hypotheses exist about the role...
A striking feature of human female sexual reproduction is the high level of gametes that exhibit an aberrant number of chromosomes (aneuploidy). A high baseline observed in women of prime reproductive age is followed by a dramatic increase in older women. Proper chromosome segregation requires one or more DNA crossovers (COs) between homologous maternal and paternal chromosomes, in combination with...
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