A comparative chromosome study on five Minnow fishes (Cyprinidae, Cypriniformes) in Thailand

The cytogenetic comparisons of five Minnow species from Thailand were presented here, i.e., Devario regina, D. laoensis, Rasbora paviana, R. aurotaenia and Esomus metalicus. The mitotic chromosomes were prepared directly from renal cells. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results revealed that all Minnow fishes studied possessed the same diploid chromosome number (2n) as 50 chromosomes. The fundamental numbers (NF) of D. laoensis, D. regina, R. paviana, R. aurotaenia and E. metalicus are 100, 100, 98, 98, and 98 respectively. Their karyotypes composing of metacentrics-submetacentrics-acrocentrics-telocentrics were as follows: 6-12-32-0 in D. regina, 6-10-34-0 in D. laoensis, 8-16-24-2 in R. paviana, 8-16-24-2 in R. aurotaenia and 8-10-30-2 in E. metalicus. The Ag-NOR banding technique provides the nucleolar organizer regions (NORs) at subtelomeric region of the short arm chromosome in the a submetacentric or acrocentric chromosomes that are located differently in the different chromosome pairs among species.

Comprehensive Analysis of Human Subtelomeres by Whole Genome Mapping

Detailed comprehensive knowledge of the structures of individual long-range telomere-terminal haplotypes are needed to understand their impact on telomere function, and to delineate the population structure and evolution of subtelomere regions. However, the abundance of large evolutionarily recent segmental duplications and high levels of large structural variations have complicated both the mapping and sequence characterization of human subtelomere regions. Here, we use high throughput optical mapping of large single DNA molecules in nanochannel arrays for 154 human genomes from 26 populations to present a comprehensive look at human subtelomere structure and variation. The results catalog many novel long-range subtelomere haplotypes and determine the frequencies and contexts of specific subtelomeric duplicons on each chromosome arm, helping to clarify the currently ambiguous nature of many specific subtelomere structures as represented in the current reference sequence (HG38). The organization and content of some duplicons in subtelomeres appear to show both chromosome arm and population-specific trends. Based upon these trends we estimate a timeline for the spread of these duplication blocks.Author SummaryThe ends of human chromosomes have caps called telomeres that are essential. These telomeres are influenced by the portions of DNA next to them, a region known as the subtelomere. We need to better understand the subtelomeric region to understand how it impacts the telomeres. This subtelomeric region is not well described in the current references. This is due to large variations in this region and portions that are repeated many times, making current sequencing technologies struggle to capture these regions. Many of these variations are evolutionary recent. Here we use 154 different samples from the 26 geographic regions of the world to gain a better understanding of the variation in these regions. We found many new haplotypes and clarified the haplotypes existing in the current reference. We then examined population and chromosome specific trends.

Characterization of eight species of Aloe (Asphodelaceae) from the nucleolar organizing region

Nucleolar organizing region of eight species of Aloe was analyzed in somatic metaphases and interphase nuclei. All species showed a uniform 2n=14, with eight large chromosomes and six small chromosomes. Satellites were observed on the long arm of one or two pairs of large chromosomes and/or on the short arm of one of the small pairs. The silver-stained nucleolus organizing regions were located on the subtelomeric region of the long arm of one or two pairs of large chromosomes, except for Aloe dichotoma and Aloe maculata, which the AgNORs were located at a short arm of one of their small chromosomes. In most studied species, the active AgNOR number was four. However, this number changing from one to eight. For all species, the interphase number of nucleoli can be one or two, while, in Aloe excelsa, this number can be changing from one to eight. Polymorphism of active AgNORs and the number of interphase nucleoli were revealed, except for Aloe petricola, which active AgNORs were located only in the subtelomeric regions at the long arm of one of the L2 chromosomes, as well as in the L4 pair, which is agrément with the maximum number (three) of interphase nucleoli.

Newly discovered genes for resistance to powdery mildew in the subtelomeric region of the short arm of barley chromosome 7H

Two dominant genes for resistance to powdery mildew (caused by Blumeria graminis f.sp. hordei) from the PI296825 and PI466461 accessions of wild barley (Hordeum vulgare subsp. spontaneum) were identified close to the subtelomeric region of the short arm of chromosome 7H. Genetic analyses predicted two resistance loci in F₂ populations established from crosses between each of the two accessions and the winter barley (H. vulgare) variety Tiffany. Genetic mapping revealed a highly effective (52% of phenotypic variation) resistance gene from PI296825 located between the markers GBMS192 and GBM1060. In F₂ plants exhibiting resistance reaction types (RT) 0 to RT1–2, specific DNA fragments for co-segregating markers were amplified. In plants with RT2 and RT2–3, the resistance was conferred by another unidentified resistance gene. In PI466461, the resistance gene found on the short arm of chromosome 7H was flanked by the markers GBM1126 and GBM1060. Another resistance gene coincided with the Mla locus. Resistance in RT0 plants was conferred by both resistance genes, which accounted for 58% of the total phenotypic variation. The two resistance genes with the same location on chromosome 7H have different phenotypic effects on the resistance in RT0 plants; therefore, the resistance alleles could be at different loci.

16P Subtelomeric Duplication With Vascular Anomalies: An Albanian Case Report And Literature Review

ABSTRACT A patient with karyotype 46,XY,der(4) was recognized by standard cytogenetic techniques, and presented with facial features, neurological impairment and pulmonary hypertension. Multiplex ligation-dependent probe amplification (MLPA) demonstrated duplication of the subtelomeric region of chromosome 16p and deletion of the subtelomeric region of chromosome 4q, suggesting a translocation between 4q and 16p. The karyotype of his parents was normal and their MLPA analysis also indicated a de novo imbalance. He had microcephaly, high frontal hairline, thin blond hair, bilateral blepharophimosis and palpebral ptosis, short nose, everted upper lip, cleft palate, micrognathia, cupped anteverted ears, hypoplastic distal phalanges and bilateral inguinal hernia. He also had pulmonary hypertension with tricuspidal regurgitation; cavernous liver hemangioma anomalies have been previously described in association with dup16p. We concluded that pulmonary and other vascular anomalies can be a feature of dup16p. We believe this is the first confirmed case of a 16p subtelomeric duplication with vascular anomalies identified in Albania.