Browsing by Author "Güngör, T."

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    Cu doping induced structural and optical properties of bimetallic oxide nanodots by the vertical spark generation
    (Polish Academy of Sciences, 2019-05) Güngör, T.; Güngör, E.; Çalışkan, Deniz; Özbay, Ekmel
    Undoped ZnO and Cu doped ZnO nanodots (NDs) were synthesized by the modified sparking technique with the Zn and Cu metal electrode pairs such as Zn–Zn, Zn–Cu and Cu–Cu. The effect of deposition geometry on the structural, optical properties and band gap energy were examined. The X-ray diffraction (XRD) analysis demonstrates that the nanodots have the hexagonal wurtzite structure, and visible considerable shift in the peaks position can be linked with the influence of Cu. However, when copper electrode was used, some copper oxide phases, metallic copper and paramelaconite phases were observed. From the results, the average diameters of metal oxide nanodots are about 25 nm and 50 nm which were obtained by using Cu–Cu and for Zn–Zn electrodes respectively from the scanning electron microscopy (SEM) analysis. When the Zn–Cu electrode pairs were used, the mixture of nanorod and nanodots appeared. It was observed that the island growth occurs in the horizontal geometry of electrode pairs and the growth metal oxide species are more strongly bonded to each other than to the substrate. But, these nanodots have more uniform distribution in the vertical geometry of electrodes. Optical studies indicated that the band gap decreased (red shift) when the Cu electrode was used.
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    Discovery and genotyping of novel sequence insertions in many sequenced individuals
    (Oxford University Press, 2017) Kavak, P.; Lin, Yen-Yi; Numanagić, I.; Asghari, H.; Güngör, T.; Alkan C.; Hach, F.
    Motivation: Despite recent advances in algorithms design to characterize structural variation using high-throughput short read sequencing (HTS) data, characterization of novel sequence insertions longer than the average read length remains a challenging task. This is mainly due to both computational difficulties and the complexities imposed by genomic repeats in generating reliable assemblies to accurately detect both the sequence content and the exact location of such insertions. Additionally, de novo genome assembly algorithms typically require a very high depth of coverage, which may be a limiting factor for most genome studies. Therefore, characterization of novel sequence insertions is not a routine part of most sequencing projects. There are only a handful of algorithms that are specifically developed for novel sequence insertion discovery that can bypass the need for the whole genome de novo assembly. Still, most such algorithms rely on high depth of coverage, and to our knowledge there is only one method (PopIns) that can use multi-sample data to "collectively" obtain a very high coverage dataset to accurately find insertions common in a given population. Result: Here, we present Pamir, a new algorithm to efficiently and accurately discover and genotype novel sequence insertions using either single or multiple genome sequencing datasets. Pamir is able to detect breakpoint locations of the insertions and calculate their zygosity (i.e. heterozygous versus homozygous) by analyzing multiple sequence signatures, matching one-end-anchored sequences to small-scale de novo assemblies of unmapped reads, and conducting strand-aware local assembly. We test the efficacy of Pamir on both simulated and real data, and demonstrate its potential use in accurate and routine identification of novel sequence insertions in genome projects.
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    Improving genome assemblies using multi-platform sequence data
    (Springer, 2015-09) Kavak, P.; Ergüner, B.; Üstek, D.; Yüksel, B.; Saǧıroǧlu, M. Ş.; Güngör, T.; Alkan, Can
    Accurate de novo assembly using short reads generated by next generation sequencing technologies is still an open problem. Although there are several assembly algorithms developed for data generated with different sequencing technologies, and some that can make use of hybrid data, the assemblies are still far from being perfect. There is still a need for computational approaches to improve draft assemblies. Here we propose a new method to correct assembly mistakes when there are multiple types of data generated using different sequencing technologies that have different strengths and biases. We exploit the assembly of highly accurate short reads to correct the contigs obtained from less accurate long reads. We apply our method to Illumina, 454, and Ion Torrent data, and also compare our results with existing hybrid assemblers, Celera and Masurca. © Springer International Publishing Switzerland 2016.
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    Robustness of massively parallel sequencing platforms
    (Public Library of Science, 2015) Kavak P.; Yüksel, B.; Aksu, S.; Kulekci, M.O.; Güngör, T.; Hach F.; Şahinalp, S.C.; Alkan, C.; Saʇiroʇlu, M.Ş.
    The improvements in high throughput sequencing technologies (HTS) made clinical sequencing projects such as ClinSeq and Genomics England feasible. Although there are significant improvements in accuracy and reproducibility of HTS based analyses, the usability of these types of data for diagnostic and prognostic applications necessitates a near perfect data generation. To assess the usability of a widely used HTS platform for accurate and reproducible clinical applications in terms of robustness, we generated whole genome shotgun (WGS) sequence data from the genomes of two human individuals in two different genome sequencing centers. After analyzing the data to characterize SNPs and indels using the same tools (BWA, SAMtools, and GATK), we observed significant number of discrepancies in the call sets. As expected, the most of the disagreements between the call sets were found within genomic regions containing common repeats and segmental duplications, albeit only a small fraction of the discordant variants were within the exons and other functionally relevant regions such as promoters. We conclude that although HTS platforms are sufficiently powerful for providing data for first-pass clinical tests, the variant predictions still need to be confirmed using orthogonal methods before using in clinical applications. © 2015 Kavak et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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    Whole genome sequencing of Turkish genomes reveals functional private alleles and impact of genetic interactions with Europe, Asia and Africa
    (BioMed Central Ltd., 2014-11-07) Alkan C.; Kavak, P.; Somel, M.; Gokcumen, O.; Ugurlu, S.; Saygi, C.; Dal, E.; Bugra, K.; Güngör, T.; Sahinalp, S. C.; Özören, N.; Bekpen, C.
    Background: Turkey is a crossroads of major population movements throughout history and has been a hotspot of cultural interactions. Several studies have investigated the complex population history of Turkey through a limited set of genetic markers. However, to date, there have been no studies to assess the genetic variation at the whole genome level using whole genome sequencing. Here, we present whole genome sequences of 16 Turkish individuals resequenced at high coverage (32 × −48×). Results: We show that the genetic variation of the contemporary Turkish population clusters with South European populations, as expected, but also shows signatures of relatively recent contribution from ancestral East Asian populations. In addition, we document a significant enrichment of non-synonymous private alleles, consistent with recent observations in European populations. A number of variants associated with skin color and total cholesterol levels show frequency differentiation between the Turkish populations and European populations. Furthermore, we have analyzed the 17q21.31 inversion polymorphism region (MAPT locus) and found increased allele frequency of 31.25% for H1/H2 inversion polymorphism when compared to European populations that show about 25% of allele frequency. Conclusion: This study provides the first map of common genetic variation from 16 western Asian individuals and thus helps fill an important geographical gap in analyzing natural human variation and human migration. Our data will help develop population-specific experimental designs for studies investigating disease associations and demographic history in Turkey.