Revision of the banding sequence pool and new data on chromosomal polymorphism in natural populations of Chironomus agilis Shobanov et Djomin, 1988 (Diptera, Chironomidae)

Quantitative and qualitative analysis of chromosomal polymorphism in 19 natural populations of Ch. agilis had been performed. Most studied populations showed a medium level of chromosomal polymorphism: on average 45±3.0% of specimens are heterozygotes with 0.52±0.01 heterozygotic inversion per larvae. Besides inversions, B-chromosomes were found in two populations. The total number of banding sequences found in banding sequence pool of Ch. agilis is 16. Three banding sequences – p’agiB3, p’agiD3, p’agiF3 – are described for the first time.

The pink salmon genome: Uncovering the genomic consequences of a two-year life cycle

Pink salmon (Oncorhynchus gorbuscha) adults are the smallest of the five Pacific salmon native to the western Pacific Ocean. Pink salmon are also the most abundant of these species and account for a large proportion of the commercial value of the salmon fishery worldwide. A two-year life history of pink salmon generates temporally isolated populations that spawn either in even-years or odd-years. To uncover the influence of this genetic isolation, reference genome assemblies were generated for each year-class and whole genome re-sequencing data was collected from salmon of both year-classes. The salmon were sampled from six Canadian rivers and one Japanese river. At multiple centromeres we identified peaks of Fst between year-classes that were millions of base-pairs long. The largest Fst peak was also associated with a million base-pair chromosomal polymorphism found in the odd-year genome near a centromere. These Fst peaks may be the result of a centromere drive or a combination of reduced recombination and genetic drift, and they could influence speciation. Other regions of the genome influenced by odd-year and even-year temporal isolation and tentatively under selection were mostly associated with genes related to immune function, organ development/maintenance, and behaviour.

A rare chromosomal polymorphism in a Kangayam bull (Bos indicus) of south India

A chromosomal polymorphism was detected on karyological screening of Kangayam breeding sires prior to subjecting them for frozen semen collection. One bull possessed the chromosomal complement 2n = 60, consisting of 58 acrocentric autosomes, one large sub-metacentric X-chromosome, and one small acrocentric Y-chromosome with a small visible p-arm, which was further confirmed using CBG- and GTG-banding. This polymorphism was attributed to a heterochromatin variation of the acrocentric Y-chromosome routine in the Bos indicus Linnaeus, 1758 cattle.

CHROMOSOMAL POLYMORPHISM IN BULGARIAN PATIENTS WITH REPRODUCTIVE PROBLEMS – ONE GENETIC CENTRE EXPERIENCE

Chromosomal polymorphism is described as normal variants at chromosomal regions with no impact on the phenotype but a possible correlation to infertility and recurrent spontaneous abortions. The aim of this study was to evaluate the effect of the chromosomal polymorphisms involved in families with reproductive failures in the Bulgarian population. Material and methods: A total of 1733 patients with unexplained reproductive failures who visited the Laboratory of Medical Genetics – Varna, Bulgaria, (2004 - 2019) were investigated by conventional cytogenetic analysis GTG and CBG differential banding techniques and analyzed at the resolution 400-550 GTG bands. Results: Chromosomal polymorphisms were found in 173 infertile patients (9,98%). The sex distribution was 6,52% males and 3,46% females. The most frequent finding was inv(9)(qh) (23,7%). The other chromosomal variants, which were found, consisted: 9qh+/- variants (15,1%); polymorphisms on the short arms of the acrocentric chromosomes (21,4%); 16qh+ (12,7%) and 1qh+ (6,9%). Y chromosome polymorphism was found in 27,4% of the males with polymorphisms. Two rare cases of polymorphism involving the centromere regions - 19qcenh+ and 20pcenh+ were also found. Conclusion: There is growing evidence that polymorphisms may have a clinical impact on fertility and could take part in the etiology of RF. In this study, we found a significantly high percentage of polymorphisms (9,98%) among the tested patients, and they were more common among males. The statistical significance of increased incidence of chromosome variations found in our study emphasizes the need for routine evaluation of their role in families with RF in our country.

Highly divergent karyotypes and barcoding of the East African genus Gonatoxia Karsch (Orthoptera: Phaneropterinae)

East Africa is a hotspot of biodiversity of many orthopteran taxa, including bushcrickets. Gonatoxia Karsch, 1889 species are fully alate Phaneropterinae, which are perfectly adapted to the foliage of forests. We examined five species using combined cytogenetic and molecular data to determine the inter- and intraspecific genetic diversity. The variation in the diploid number of chromosomes in males ranged from 2n = 28 + X0 and 26 + X0 to 2n = 6 + X0. Fluorescence in situ hybridization showed from one to many 18S rDNA loci as well as interstitial sequences, especially in G. helleri. 18S rDNA loci coincided with active NOR and C-banding patterns. The isolation of populations of the species explains differences in the number of chromosomes (G. maculata), chromosomal polymorphism and chromosomal heterozygosity (G. helleri). Our molecular phylogeny based on the COI locus supported the monophyly of the genus Gonatoxia and separateness of the five examined species in accordance with their morphological features and chromosome numbers as well as the species’ distribution.

The pink salmon genome: uncovering the genomic consequences of a strict two-year life-cycle

Pink salmon (Oncorhynchus gorbuscha) adults are the smallest of the five Pacific salmon native to the western Pacific Ocean. Pink salmon are also the most abundant of these species and account for a large proportion of the commercial value of the salmon fishery worldwide. A strict two-year life-history of most pink salmon generates temporally isolated populations that spawn either in even-years or odd-years. To uncover the influence of this genetic isolation, reference genome assemblies were generated for each year-class and whole genome re-sequencing data was collected from salmon of both year-classes. The salmon were sampled from six Canadian rivers and one Japanese river. At multiple centromeres we identified peaks of Fst between year-classes that were millions of base-pairs long. The largest Fst peak was also associated with a million base-pair chromosomal polymorphism found in the odd-year genome near a centromere. These Fst peaks may be the result of centromere drive or a combination of reduced recombination and genetic drift, and they could influence speciation. Other regions of the genome influenced by odd-year and even-year temporal isolation and tentatively under selection were mostly associated with genes related to immune function, organ development/maintenance, and behaviour.

Unusual chromosomal polymorphism of the common shrew, Sorex araneus L., in southern Belarus

Analysis of the frequency of karyotypes and chromosomal rearrangements in the distributional ranges of four metacentric races of Sorex araneus Linnaeus, 1758 has revealed features that are not typical for polymorphic populations of this species. The frequency of the acrocentric karyotype and heterozygotes for fusion of acrocentric chromosomes turned out to be significantly higher than expected in case of random crossing. As an explanation for the unusual polymorphism, it has been suggested that metacentric races may hybridize with acrocentric populations that remained from the ancient chromosomal form.

Peculiarities of karyotype of the Ukrainian aboriginal Hutsul breed of horse

Saving biodiversity and assessment of the genetic diversity of local breeds of domestic animals as priority subjects of protection in agrobiocenoses is one of the global challenges facing humanity in the 21st century. Hutsul horse is one of the oldest horse breeds in Ukraine, which according to the gene pool subject of horses in Ukraine belongs to the group “Local (mountain and ponies)” of the I category, which is already on the verge of extinction, and according to the FAO classification it is considered to be a subject of the gene pool threatened with extinction. Since the breeding chromosomal polymorphism of horses is insufficiently studied, it is timely to carry out a cytogenetic analysis of the characteristics of spontaneous mutagenesis in Hutsul horses. Karyotypic variability of Hutsul breed horses was determined using the methods of cytogenetic analysis and micronucleus test. The paper presents the results of cytogenetic analysis and micronucleus test of karyotypic variability of Hutsul breed horses. Asynchronous divergence of centromere regions of chromosomes occurs as a result of premature replication of centromere regions of heterochromatin associated with centromere activity. In the studied Hutsul horses, the magnitude of this variability corresponds to the spontaneous level for horses as a whole (2.2-9.1 %). No structural chromosomal abnormalities (chromosomal breaks) were revealed in Hutsul breed horses at Krai Neba LLC, and in the animals of the Hutsulshchina National Nature Park, the percentage of metaphase plates with chromosomal breaks was low (1.1 %), which indicates the stability of the karyotype of the studied animals. The results of the micronucleus test showed that the proportion of lymphocytes with micronuclei in the animals at the both farms was practically the same - 4.0-4.2. It can be concluded based on the data obtained that the animals under study were in ecologically clean conditions relative to the level of radionuclide contamination and were characterized by karyotype stability and reduced sensitivity to mutagenic factors of various nature.