Cytological Analysis of Crossover Frequency and Distribution in Male Meiosis of Cardueline Finches (Fringillidae, Aves).

Meiotic recombination is an important source of genetic diversity. Using immunolocalization of several meiotic proteins at the spreads of male pachytene cells, we estimated the number of recombination nodules per cell and their distribution along the macrochromosome 1 of the , , , and . The macrochromosomes of the two former species have metapolycentromeres, composed of several centromeric domains.

Chromosome Asynapsis Is the Main Cause of Male Sterility in the Interspecies Hybrids of East Asian Voles (, Rodentia, Arvicolinae).

Closely related mammalian species often have differences in chromosome number and morphology, but there is still a debate about how these differences relate to reproductive isolation. To study the role of chromosome rearrangements in speciation, we used the gray voles in the genus as a model. These voles have a high level of chromosome polymorphism and substantial karyotypic divergence.

Mendelian nightmares: the germline-restricted chromosome of songbirds.

Germline-restricted chromosomes (GRCs) are accessory chromosomes that occur only in germ cells. They are eliminated from somatic cells through programmed DNA elimination during embryo development. GRCs have been observed in several unrelated animal taxa and show peculiar modes of non-Mendelian inheritance and within-individual elimination.

Germline-Restricted Chromosome (GRC) in Female and Male Meiosis of the Great Tit (Parus major, Linnaeus, 1758).

All songbirds studied so far have a germline-restricted chromosome (GRC), which is present in the germ cells and absent in the somatic cells. It shows a wide variation in size, morphology, and genetic content between the songbird species. In this paper, we analyzed GRC behavior in female and male meiosis of the great tit, using immunolocalization of meiotic proteins and FISH with GRC-derived DNA probes.

Highly Conservative Pattern of Sex Chromosome Synapsis and Recombination in Neognathae Birds.

We analyzed the synapsis and recombination between Z and W chromosomes in the oocytes of nine neognath species: domestic chicken , grey goose , black tern , common tern , pale martin , barn swallow , European pied flycatcher great tit and white wagtail using immunolocalization of SYCP3, the main protein of the lateral elements of the synaptonemal complex, and MLH1, the mismatch repair protein marking mature recombination nodules. In all species examined, homologous synapsis occurs in a short region of variable size at the ends of Z and W chromosomes, where a single recombination nodule is located. The remaining parts of the sex chromosomes undergo synaptic adjustment and synapse non-homologously.

Heterochiasmy and Sexual Dimorphism: The Case of the Barn Swallow (, Hirundinidae, Aves).

Heterochiasmy, a sex-based difference in recombination rate, has been detected in many species of animals and plants. Several hypotheses about evolutionary causes of heterochiasmy were proposed. However, there is a shortage of empirical data.

Prioritization of causal genes for coronary artery disease based on cumulative evidence from experimental and in silico studies.

Genome-wide association studies have led to a significant progress in identification of genomic loci affecting coronary artery disease (CAD) risk. However, revealing the causal genes responsible for the observed associations is challenging. In the present study, we aimed to prioritize CAD-relevant genes based on cumulative evidence from the published studies and our own study of colocalization between eQTLs and loci associated with CAD using SMR/HEIDI approach.

Germline-restricted chromosome (GRC) in the sand martin and the pale martin (Hirundinidae, Aves): synapsis, recombination and copy number variation.

All songbirds studied to date have an additional Germline Restricted Chromosome (GRC), which is not present in somatic cells. GRCs show a wide variation in genetic content and little homology between species. To check how this divergence affected the meiotic behavior of the GRC, we examined synapsis, recombination and copy number variation for GRCs in the closely related sand and pale martins (Riparia riparia and R.

Spatial organization of fibroblast and spermatocyte nuclei with different B-chromosome content in Korean field mouse, Apodemus peninsulae (Rodentia, Muridae).

Korean field mouse (Apodemus peninsulae) shows a wide variation in the number of B chromosomes composed of constitutive heterochromatin. For this reason, it provides a good model to study the influence of the number of centromeres and amount of heterochromatin on spatial organization of interphase nuclei. We analyzed the three-dimensional organization of fibroblast and spermatocyte nuclei of the field mice carrying a different number of B chromosomes using laser scanning microscopy and 3D fluorescence in situ hybridization.

Immunocytological Analysis of Meiotic Recombination in the Gray Goose (Anser anser).

Studies on mammals demonstrate wide interspecific variation in the number and distribution of recombination events along chromosomes. Birds represent an interesting model group for comparative analysis of cytological and ecological drivers of recombination rate evolution. Yet, data on variation in recombination rates in birds are limited to a dozen of species.

Chromosome synapsis and recombination in simple and complex chromosomal heterozygotes of tuco-tuco (Ctenomys talarum: Rodentia: Ctenomyidae).

The chromosomal speciation hypothesis suggests that irregularities in synapsis, recombination, and segregation in heterozygotes for chromosome rearrangements may restrict gene flow between karyotypically distinct populations and promote speciation. Ctenomys talarum is a South American subterranean rodent inhabiting the coastal regions of Argentina, whose populations polymorphic for Robertsonian and tandem translocations seem to have a very restricted gene flow. To test if chromosomal differences are involved in isolation among its populations, we examined chromosome pairing, recombination, and meiotic silencing of unsynapsed chromatin in male meiosis of simple and complex translocation heterozygotes using immunolocalization of the MLH1 marking mature recombination nodules and phosphorylated histone γH2A.

Recombination and synaptic adjustment in oocytes of mice heterozygous for a large paracentric inversion.

Homologous chromosome synapsis in inversion heterozygotes results in the formation of inversion loops. These loops might be transformed into straight, non-homologously paired bivalents via synaptic adjustment. Synaptic adjustment was discovered 30 years ago; however, its relationship with recombination has remained unclear.

Multiple independent evolutionary losses of XY pairing at meiosis in the grey voles.

In many eutherian mammals, X-Y chromosome pairing and recombination is required for meiotic progression and correct sex chromosome disjunction. Arvicoline rodents present a notable exception to this meiotic rule, with multiple species possessing asynaptic sex chromosomes. Most asynaptic vole species belong to the genus Microtus sensu lato.

Synapsis and recombination in inversion heterozygotes.

Inversion heterozygotes are expected to suffer from reduced fertility and a high incidence of chromosomally unbalanced gametes due to recombination within the inverted region. Non-homologous synapsis of the inverted regions can prevent recombination there and diminish the deleterious effects of inversion heterozygosity. The choice between non-homologous and homologous synapsis depends on the size of inversion, its genetic content, its location in relation to the centromere and telomere, and genetic background.

A- and B-chromosome pairing and recombination in male meiosis of the silver fox (Vulpes vulpes L., 1758, Carnivora, Canidae).

We examined A- and B-chromosome pairing and recombination in 12 males from the farm-bred population of the silver fox (2n = 34 + 0-10 Bs) by means of electron and immunofluorescent microscopy. To detect recombination at A and B chromosomes, we used immunolocalisation of MLH1, a mismatch repair protein of mature recombination nodules, at synaptonemal complexes. The mean total number of MLH1 foci at A-autosomes was 29.

Recombination map of the common shrew, Sorex araneus (Eulipotyphla, Mammalia).

The Eurasian common shrew (Sorex araneus L.) is characterized by spectacular chromosomal variation, both autosomal variation of the Robertsonian type and an XX/XY(1)Y(2) system of sex determination. It is an important mammalian model of chromosomal and genome evolution as it is one of the few species with a complete genome sequence.