Genomes 3 Ebook Free 22
Kym Cavrak
The ability to characterize microbial genomes is advancing many fields of research. In fact, sequencing approaches now allow scientists to understand disease origins and anticipate transmission patterns with applications across human health, farming and food production industries.
Until recently, large eukaryotic genomes have proved challenging to sequence and assemble with traditional sequencing methods. Full characterization of plant and animal genomes via high-throughput sequencing is revolutionizing many areas of research. In human and veterinary health, sequencing enables unprecedented insights into disease, whilst investigating genetic variation in plants allows for the maintenance of diversity and selection of desirable traits, such as high yield and resistance to pathogens. With nanopore sequencing, large genomes can be sequenced in fewer, longer fragments, allowing easier genome assembly and resolution of even the most challenging regions.
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This book highlights the uses for underutilized crops, presenting the state-of-the-art in terms of genome sequencing for over 30 crops, previously understudied and under-researched. In a changing climate and with significant pressure on the land, it is the ideal time to be discussing novel crops, with significant biotic and abiotic tolerances and/or rich nutrient profiles for consumers. Previously, the only species with sequenced genomes were high-profile internationally recognized crops, but in the current era genomes are being sequenced for dozens of crops, including those previously classified as underutilized, now being investigated. This book covers food crops, from fruits to tubers, and from grasses to legumes, as well as crops with non-food applications. Some of these crops have draft genomes, and others have polished genomes with extensive resequencing panels. Each chapter tells the story of an individual crop or crop group, written by experts, focusing on the genome data available, revealing more about crop domestication and genetic variation, and the current and future prospects given that this data is now becoming available. It also highlights how even small sequencing projects can provide draft genome sequences suitable for gene discovery, comparative genomics, and identification of molecular markers for understanding these crops further.
Genomes 5 has been completely revised and updated. It is a thoroughly modern textbook about genomes and how they are investigated. As with previous Genomes editions, techniques come first, then genome anatomies, followed by genome function, and finally genome evolution. The genomes of all types of organism are covered: viruses, bacteria, fungi, plants, and animals, including humans and other hominids.
Genome sequencing and assembly methods have been thoroughly revised to include new developments in long-read DNA sequencing. Coverage of genome annotation emphasizes genome-wide RNA mapping, with CRISPR-Cas 9 and GWAS methods of determining gene function covered. The knowledge gained from these techniques forms the basis of the chapters that describe the three main types of genomes: eukaryotic, prokaryotic (including eukaryotic organelles), and viral (including mobile genetic elements). Coverage of genome expression and replication is truly genomic, concentrating on the genome-wide implications of DNA packaging, epigenome modifications, DNA-binding proteins, non-coding RNAs, regulatory genome sequences, and protein-protein interactions. Also included are examples of the applications of metabolomics and systems biology. The final chapter is on genome evolution, including the evolution of the epigenome, using genomics to study human evolution, and using population genomics to advance plant breeding. Established methods of molecular biology are included if they are still relevant today and there is always an explanation as to why the method is still important.
It is important to consider how the genome is similar to other genomes that are already known, as this can help when establishing the role of the gene. Additionally, the plasmids, phages and resistance genes of the genome can reveal information about the nature of the genome.
As a key component of the HGP, it was wisely decided to sequence the smaller genomes of significant experimental model organisms such as yeast, a small flowering plant (Arabidopsis thaliana), worm and fruit fly before taking on the far more challenging human genome. The efforts of multiple centers were integrated to produce these reference genome sequences, fostering a culture of cooperation. There were originally 20 centers mapping and sequencing the human genome as part of an international consortium [18]; in the end five large centers (the Wellcome Trust Sanger Institute, the Broad Institute of MIT and Harvard, The Genome Institute of Washington University in St Louis, the Joint Genome Institute, and the Whole Genome Laboratory at Baylor College of Medicine) emerged from this effort, with these five centers continuing to provide genome sequence and technology development. The HGP also fostered the development of mathematical, computational and statistical tools for handling all the data it generated.
Third, our understanding of evolution has been transformed. Since the completion of the HGP, over 4,000 finished or quality draft genome sequences have been produced, mostly from bacterial species but including 183 eukaryotes [31]. These genomes provide insights into how diverse organisms from microbes to human are connected on the genealogical tree of life - clearly demonstrating that all of the species that exist today descended from a single ancestor [32]. Questions of longstanding interest with implications for biology and medicine have become approachable. Where do new genes come from? What might be the role of stretches of sequence highly conserved across all metazoa? How much large-scale gene organization is conserved across species and what drives local and global genome reorganization? Which regions of the genome appear to be resistant (or particularly susceptible) to mutation or highly susceptible to recombination? How do regulatory networks evolve and alter patterns of gene expression [33]? The latter question is of particular interest now that the genomes of several primates and hominids have been or are being sequenced [34, 35] in hopes of shedding light on the evolution of distinctively human characteristics. The sequence of the Neanderthal genome [36] has had fascinating implications for human evolution; namely, that a few percent of Neanderthal DNA and hence the encoded genes are intermixed in the human genome, suggesting that there was some interbreeding while the two species were diverging [36, 37].
Five years ago, a mere handful of personal genomes had been fully sequenced (for example, [53, 54]). Now there are thousands of exome and whole-genome sequences (soon to be tens of thousands, and eventually millions), which have been determined with the aim of identifying disease-causing variants and, more broadly, establishing well-founded correlations between sequence variation and specific phenotypes. For example, the International Cancer Genome Consortium [55] and The Cancer Genome Atlas [56] are undertaking large-scale genomic data collection and analyses for numerous cancer types (sequencing both the normal and cancer genome for each individual patient), with a commitment to making their resources available to the research community.
The HGP infused a technological capacity into biology that has resulted in enormous increases in the range of research, for both big and small science. Experiments that were inconceivable 20 years ago are now routine, thanks to the proliferation of academic and commercial wet lab and bioinformatics resources geared towards facilitating research. In particular, rapid increases in throughput and accuracy of the massively parallel second-generation sequencing platforms with their correlated decreases in cost of sequencing have resulted in a great wealth of accessible genomic and transcriptional sequence data for myriad microbial, plant and animal genomes. These data in turn have enabled large- and small-scale functional studies that catalyze and enhance further research when the results are provided in publicly accessible databases [70].
Newer generations of DNA sequencing platforms will be introduced that will transform how we gather genome information. Third-generation sequencing [74] will employ nanopores or nanochannels, utilize electronic signals, and sequence single DNA molecules for read lengths of 10,000 to 100,000 bases. Third-generation sequencing will solve many current problems with human genome sequences. First, contemporary short-read sequencing approaches make it impossible to assemble human genome sequences de novo; hence, they are usually compared against a prototype reference sequence that is itself not fully accurate, especially with respect to variations other than SNPs. This makes it extremely difficult to precisely identify the insertion-deletion and structural variations in the human genome, both for our species as a whole and for any single individual. The long reads of third-generation sequencing will allow for the de novo assembly of human (and other) genomes, and hence delineate all of the individually unique variability: nucleotide substitutions, indels, and structural variations. Second, we do not have global techniques for identifying the 16 different chemical modifications of human DNA (epigenetic marks, reviewed in [75]). It is increasingly clear that these epigenetic modifications play important roles in gene expression [76]. Thus, single-molecule analyses should be able to identify all the epigenetic marks on DNA. Third, single-molecule sequencing will facilitate the full-length sequencing of RNAs; thus, for example, enhancing interpretation of the transcriptome by enabling the identification of RNA editing, alternative splice forms with a given transcript, and different start and termination sites. Last, it is exciting to contemplate that the ability to parallelize this process (for example, by generating millions of nanopores that can be used simultaneously) could enable the sequencing of a human genome in 15 minutes or less [77]. The high-throughput nature of this sequencing may eventually lead to human genome costs of $100 or under. The interesting question is how long it will take to make third-generation sequencing a mature technology.
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