scholarly journals Education in the genomics era: Generating high-quality genome assemblies in university courses

GigaScience ◽  
2020 ◽  
Vol 9 (6) ◽  
Author(s):  
Stefan Prost ◽  
Sven Winter ◽  
Jordi De Raad ◽  
Raphael T F Coimbra ◽  
Magnus Wolf ◽  
...  
Keyword(s):  
Low Cost ◽  
Genomic Data ◽  
Master's Level ◽  
Genome Data ◽  
Sequencing Technologies ◽  
Third Generation Sequencing ◽  
University Courses ◽  
Hands On ◽  
Genome Assemblies ◽  
High Quality Genome

Abstract Recent advances in genome sequencing technologies have simplified the generation of genome data and reduced the costs for genome assemblies, even for complex genomes like those of vertebrates. More practically oriented genomic courses can prepare university students for the increasing importance of genomic data used in biological and medical research. Low-cost third-generation sequencing technology, along with publicly available data, can be used to teach students how to process genomic data, assemble full chromosome-level genomes, and publish the results in peer-reviewed journals, or preprint servers. Here we outline experiences gained from 2 master's-level courses and discuss practical considerations for teaching hands-on genome assembly courses.

scholarly journals A strategy for complete telomere-to-telomere assembly of ciliate macronuclear genome using ultra-high coverage Nanopore data

2020 ◽  
Author(s):  
Guangying Wang ◽  
Xiaocui Chai ◽  
Jing Zhang ◽  
Wentao Yang ◽  
Chuanqi Jiang ◽  
...  
Keyword(s):  
High Coverage ◽  
Genome Data ◽  
Sequencing Technologies ◽  
Simple Strategy ◽  
Third Generation Sequencing ◽  
Population Genomic ◽  
Ciliate Species ◽  
Genomic Studies ◽  
High Quality Genome ◽  
Generation Sequencing

ABSTRACTCiliates contain two kinds of nuclei: the germline micronucleus (MIC) and the somatic macronucleus (MAC) in a single cell. The MAC usually have fragmented chromosomes. These fragmented chromosomes, capped with telomeres at both ends, could be gene size to several megabases in length among different ciliate species. So far, no telomere-to-telomere assembly of entire MAC genome in ciliate species is finished. Development of the third generation sequencing technologies allows to generate sequencing reads up to megabases in length that could possibly span an entire MAC chromosome. Taking advantage of ultra-long Nanopore reads, we established a simple strategy for the complete assembly of ciliate MAC genomes. Using this strategy, we assembled the complete MAC genomes of two ciliate species Tetrahymena thermophila and Tetrahymena shanghaiensis, composed of 181 and 214 chromosomes telomere-to-telomere respectively. The established strategy as well as the high-quality genome data will provide a useful approach for ciliate genome assembly, and a valuable community resource for further biological, evolutionary and population genomic studies.

scholarly journals Bridging the Gap between Vertebrate Cytogenetics and Genomics with Single-Chromosome Sequencing (ChromSeq)

Genes ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 124
Author(s):  
Alessio Iannucci ◽  
Alexey I. Makunin ◽  
Artem P. Lisachov ◽  
Claudio Ciofi ◽  
Roscoe Stanyon ◽  
...  
Keyword(s):  
Genome Evolution ◽  
Karyotype Evolution ◽  
Genomic Data ◽  
Anolis Carolinensis ◽  
Vertebrate Genome ◽  
Single Chromosome ◽  
Sequencing Technologies ◽  
Novel Approaches ◽  
Genome Assemblies ◽  
Generation Sequencing

The study of vertebrate genome evolution is currently facing a revolution, brought about by next generation sequencing technologies that allow researchers to produce nearly complete and error-free genome assemblies. Novel approaches however do not always provide a direct link with information on vertebrate genome evolution gained from cytogenetic approaches. It is useful to preserve and link cytogenetic data with novel genomic discoveries. Sequencing of DNA from single isolated chromosomes (ChromSeq) is an elegant approach to determine the chromosome content and assign genome assemblies to chromosomes, thus bridging the gap between cytogenetics and genomics. The aim of this paper is to describe how ChromSeq can support the study of vertebrate genome evolution and how it can help link cytogenetic and genomic data. We show key examples of ChromSeq application in the refinement of vertebrate genome assemblies and in the study of vertebrate chromosome and karyotype evolution. We also provide a general overview of the approach and a concrete example of genome refinement using this method in the species Anolis carolinensis.

scholarly journals ntJoin: Fast and lightweight assembly-guided scaffolding using minimizer graphs

2020 ◽  
Author(s):  
Lauren Coombe ◽  
Vladimir Nikolić ◽  
Justin Chu ◽  
Inanc Birol ◽  
René L. Warren
Keyword(s):  
Reference Sequence ◽  
Biological Research ◽  
Closely Related Species ◽  
Draft Assembly ◽  
Short Read ◽  
Sequencing Technologies ◽  
Long Read ◽  
Genome Assemblies ◽  
High Quality Genome ◽  
Reference Human Genome

AbstractSummaryThe ability to generate high-quality genome sequences is cornerstone to modern biological research. Even with recent advancements in sequencing technologies, many genome assemblies are still not achieving reference-grade. Here, we introduce ntJoin, a tool that leverages structural synteny between a draft assembly and reference sequence(s) to contiguate and correct the former with respect to the latter. Instead of alignments, ntJoin uses a lightweight mapping approach based on a graph data structure generated from ordered minimizer sketches. The tool can be used in a variety of different applications, including improving a draft assembly with a reference-grade genome, a short read assembly with a draft long read assembly, and a draft assembly with an assembly from a closely-related species. When scaffolding a human short read assembly using the reference human genome or a long read assembly, ntJoin improves the NGA50 length 23- and 13-fold, respectively, in under 13 m, using less than 11 GB of RAM. Compared to existing reference-guided assemblers, ntJoin generates highly contiguous assemblies faster and using less memory.Availability and implementationntJoin is written in C++ and Python, and is freely available at https://github.com/bcgsc/[email protected]

scholarly journals Phylogenomics of 42 tomato chloroplasts using assembly and alignment-free method

2017 ◽  
Author(s):  
Raúl Amado Cattáneo ◽  
Luis Diambra ◽  
Andrés Norman McCarthy
Keyword(s):  
Dna Sequences ◽  
Evolutionary Biology ◽  
Low Frequency ◽  
Genomic Data ◽  
Data Sets ◽  
High Coverage ◽  
Genome Data ◽  
Sequencing Technologies ◽  
Alignment Free ◽  
Chloroplast Phylogeny

Phylogenetics and population genetics are central disciplines in evolutionary biology. Both are based on the comparison of single DNA sequences, or a concatenation of a number of these. However, with the advent of next-generation DNA sequencing technologies, the approaches that consider large genomic data sets are of growing importance for the elucidation of evolutionary relationships among species. Among these approaches, the assembly and alignment-free methods which allow an efficient distance computation and phylogeny reconstruction are of great importance. However, it is not yet clear under what quality conditions and abundance of genomic data such methods are able to infer phylogenies accurately. In the present study we assess the method originally proposed by Fan et al. for whole genome data, in the elucidation of Tomatoes' chloroplast phylogenetics using short read sequences. We find that this assembly and alignment-free method is capable of reproducing previous results under conditions of high coverage, given that low frequency k-mers (i.e. error prone data) are effectively filter out. Finally, we present a complete chloroplast phylogeny for the best data quality candidates of the recently published 360 tomato genomes.

scholarly journals SeqDev: An Algorithm for Constructing Genetic Elements Using Comparative Assembly

2016 ◽  
Vol 26 (1) ◽  
pp. 105-121
Author(s):  
Tasnim Rahman ◽  
Hasnain Heickal ◽  
Shamira Tabrejee ◽  
Md Miraj Kobad Chowdhury ◽  
Sheikh Muhammad Sarwar ◽  
...  
Keyword(s):  
Low Cost ◽  
Promoter Sequence ◽  
Japonica Rice ◽  
Promoter Sequences ◽  
Genome Data ◽  
Sequencing Technologies ◽  
Wet Lab ◽  
Reference Sequences ◽  
Comparative Assembly ◽  
Generation Sequencing

With the availability of recent next generation sequencing technologies and their low cost, genomes of different organisms are being sequenced frequently. Therefore, quick assembly of genome, transcriptome, and target contigs from the raw data generated through the sequencing technologies has become necessary for better understanding of different biological systems. This article proposes an algorithm, namely SeqDev (Sequence Developer) for constructing contigs from raw reads using reference sequences. For this, we considered a weighted frequency?based consensus mechanism named BlastAssemb for primary construction of a sequence with gaps. Then, we adopted suffix array and proposed a gap filling search (GFS) algorithm for searching the missing sequences in the primary construct. For evaluating our algorithm, we have chosen Pokkali (rice) raw genome and Japonica (rice) as our reference data. Experimental results demonstrated that our proposed algorithm accurately constructs promoter sequences of Pokkali from its raw genome data. These constructed promoter sequences were 93 ? 100% identical with the reference and also aligned with 96 ? 100% of corresponding reference sequences with eValue ranging from 0.0 ? 2e-14. All these results indicated that our proposed method could be a potential algorithm to construct target contigs from raw sequences with the help of reference sequences. Further wet lab validation with specific Pokkali promoter sequence will boost this method as a robust algorithm for target contig assembly.Plant Tissue Cult. & Biotech. 26(1): 105-121, 2016 (June)

scholarly journals Phylogenomics of 42 tomato chloroplasts using assembly and alignment-free method

2017 ◽  
Author(s):  
Raúl Amado Cattáneo ◽  
Luis Diambra ◽  
Andrés Norman McCarthy
Keyword(s):  
Dna Sequences ◽  
Evolutionary Biology ◽  
Low Frequency ◽  
Genomic Data ◽  
Data Sets ◽  
High Coverage ◽  
Genome Data ◽  
Sequencing Technologies ◽  
Alignment Free ◽  
Chloroplast Phylogeny

Phylogenetics and population genetics are central disciplines in evolutionary biology. Both are based on the comparison of single DNA sequences, or a concatenation of a number of these. However, with the advent of next-generation DNA sequencing technologies, the approaches that consider large genomic data sets are of growing importance for the elucidation of evolutionary relationships among species. Among these approaches, the assembly and alignment-free methods which allow an efficient distance computation and phylogeny reconstruction are of great importance. However, it is not yet clear under what quality conditions and abundance of genomic data such methods are able to infer phylogenies accurately. In the present study we assess the method originally proposed by Fan et al. for whole genome data, in the elucidation of Tomatoes' chloroplast phylogenetics using short read sequences. We find that this assembly and alignment-free method is capable of reproducing previous results under conditions of high coverage, given that low frequency k-mers (i.e. error prone data) are effectively filter out. Finally, we present a complete chloroplast phylogeny for the best data quality candidates of the recently published 360 tomato genomes.

scholarly journals Comparative Annotation Toolkit (CAT) - simultaneous clade and personal genome annotation

2017 ◽  
Author(s):  
Ian T. Fiddes ◽  
Joel Armstrong ◽  
Mark Diekhans ◽  
Stefanie Nachtweide ◽  
Zev N. Kronenberg ◽  
...  
Keyword(s):  
Genome Annotation ◽  
De Novo ◽  
Low Cost ◽  
Great Apes ◽  
Personal Genome ◽  
Sequencing Technologies ◽  
Human Genomes ◽  
Long Read ◽  
Genome Assemblies ◽  
Rat Genome

ABSTRACTThe recent introductions of low-cost, long-read, and read-cloud sequencing technologies coupled with intense efforts to develop efficient algorithms have made affordable, high-quality de novo sequence assembly a realistic proposition. The result is an explosion of new, ultra-contiguous genome assemblies. To compare these genomes we need robust methods for genome annotation. We describe the fully open source Comparative Annotation Toolkit (CAT), which provides a flexible way to simultaneously annotate entire clades and identify orthology relationships. We show that CAT can be used to improve annotations on the rat genome, annotate the great apes, annotate a diverse set of mammals, and annotate personal, diploid human genomes. We demonstrate the resulting discovery of novel genes, isoforms and structural variants, even in genomes as well studied as rat and the great apes, and how these annotations improve cross-species RNA expression experiments.

scholarly journals The genome polishing tool POLCA makes fast and accurate corrections in genome assemblies

2019 ◽  
Author(s):  
Aleksey V. Zimin ◽  
Steven L. Salzberg
Keyword(s):  
Error Rate ◽  
Low Cost ◽  
Simulated Data ◽  
Real Data ◽  
Hybrid Strategy ◽  
Short Read ◽  
Sequencing Technologies ◽  
Long Reads ◽  
Genome Assemblies ◽  
Polishing Tool

AbstractThe introduction of third-generation DNA sequencing technologies in recent years has allowed scientists to generate dramatically longer sequence reads, which when used in whole-genome sequencing projects have yielded better repeat resolution and far more contiguous genome assemblies. While the promise of better contiguity has held true, the relatively high error rate of long reads, averaging 8–15%, has made it challenging to generate a highly accurate final sequence. Current long-read sequencing technologies display a tendency toward systematic errors, in particular in homopolymer regions, which present additional challenges. A cost-effective strategy to generate highly contiguous assemblies with a very low overall error rate is to combine long reads with low-cost short-read data, which currently have an error rate below 0.5%. This hybrid strategy can be pursued either by incorporating the short-read data into the early phase of assembly, during the read correction step, or by using short reads to “polish” the consensus built from long reads. In this report, we present the assembly polishing tool POLCA (POLishing by Calling Alternatives) and compare its performance with two other popular polishing programs, Pilon and Racon. We show that on simulated data POLCA is more accurate than Pilon, and comparable in accuracy to Racon. On real data, all three programs show similar performance, but POLCA is consistently much faster than either of the other polishing programs.

scholarly journals Progressive Cactus is a multiple-genome aligner for the thousand-genome era

Nature ◽  
2020 ◽  
Vol 587 (7833) ◽  
pp. 246-251 ◽  
Author(s):  
Joel Armstrong ◽  
Glenn Hickey ◽  
Mark Diekhans ◽  
Ian T. Fiddes ◽  
Adam M. Novak ◽  
...  
Keyword(s):  
Large Scale ◽  
De Novo ◽  
Genome Alignment ◽  
Vertebrate Genome ◽  
Multiple Genome ◽  
Sequencing Technologies ◽  
Third Generation Sequencing ◽  
Genome Assemblies ◽  
Information Database ◽  
Generation Sequencing

AbstractNew genome assemblies have been arriving at a rapidly increasing pace, thanks to decreases in sequencing costs and improvements in third-generation sequencing technologies1–3. For example, the number of vertebrate genome assemblies currently in the NCBI (National Center for Biotechnology Information) database4 increased by more than 50% to 1,485 assemblies in the year from July 2018 to July 2019. In addition to this influx of assemblies from different species, new human de novo assemblies5 are being produced, which enable the analysis of not only small polymorphisms, but also complex, large-scale structural differences between human individuals and haplotypes. This coming era and its unprecedented amount of data offer the opportunity to uncover many insights into genome evolution but also present challenges in how to adapt current analysis methods to meet the increased scale. Cactus6, a reference-free multiple genome alignment program, has been shown to be highly accurate, but the existing implementation scales poorly with increasing numbers of genomes, and struggles in regions of highly duplicated sequences. Here we describe progressive extensions to Cactus to create Progressive Cactus, which enables the reference-free alignment of tens to thousands of large vertebrate genomes while maintaining high alignment quality. We describe results from an alignment of more than 600 amniote genomes, which is to our knowledge the largest multiple vertebrate genome alignment created so far.

scholarly journals ntJoin: Fast and lightweight assembly-guided scaffolding using minimizer graphs

2020 ◽  
Vol 36 (12) ◽  
pp. 3885-3887 ◽  
Author(s):  
Lauren Coombe ◽  
Vladimir Nikolić ◽  
Justin Chu ◽  
Inanc Birol ◽  
René L Warren
Keyword(s):  
Reference Sequence ◽  
Supplementary Information ◽  
Biological Research ◽  
Closely Related Species ◽  
Draft Assembly ◽  
Short Read ◽  
Sequencing Technologies ◽  
Long Read ◽  
Genome Assemblies ◽  
High Quality Genome

Abstract Summary The ability to generate high-quality genome sequences is cornerstone to modern biological research. Even with recent advancements in sequencing technologies, many genome assemblies are still not achieving reference-grade. Here, we introduce ntJoin, a tool that leverages structural synteny between a draft assembly and reference sequence(s) to contiguate and correct the former with respect to the latter. Instead of alignments, ntJoin uses a lightweight mapping approach based on a graph data structure generated from ordered minimizer sketches. The tool can be used in a variety of different applications, including improving a draft assembly with a reference-grade genome, a short-read assembly with a draft long-read assembly and a draft assembly with an assembly from a closely related species. When scaffolding a human short-read assembly using the reference human genome or a long-read assembly, ntJoin improves the NGA50 length 23- and 13-fold, respectively, in under 13 m, using <11 GB of RAM. Compared to existing reference-guided scaffolders, ntJoin generates highly contiguous assemblies faster and using less memory. Availability and implementation ntJoin is written in C++ and Python and is freely available at https://github.com/bcgsc/ntjoin. Supplementary information Supplementary data are available at Bioinformatics online.

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