Why genome sequencing is important

How does DNA sequencing work? How does the sequencing machine know whether a base is an A, C, G, or T? What happens after DNA sequences come out of the sequencing machines? How do you assemble a genome? How do scientists know if a genome sequence is right?

What makes sequencing the human genome different from sequencing other genomes? When is a genome sequence done?

What's a genome map? What are genome variations? The human genome is made up of over 3 billion of these genetic letters. Much as your eye scans a sequence of letters to read a sentence, these machines "read" a sequence of DNA bases. A DNA sequence that has been translated from life's chemical alphabet into our alphabet of written letters might look like this:. That is, in this particular piece of DNA, an adenine A is followed by a guanine G , which is followed by a thymine T , which in turn is followed by a cytosine C , another cytosine C , and so on.

By itself, not a whole lot. Genome sequencing is often compared to "decoding," but a sequence is still very much in code. In a sense, a genome sequence is simply a very long string of letters in a mysterious language.

Better analysis tools and a deeper understanding of the biology of our genome are necessary in order to decipher, interpret, and optimize clinical utility of what the variation in the human genome can teach us. Personal genome sequencing may eventually become an instrument of common medical practice, providing information that assists in the formulation of a differential diagnosis. Whole genome pyrosequencing of rare hepatitis C virus genotypes enhances subtype classification and identification of naturally occurring drug resistance variants.

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Feehery, G. Download references. The authors thank J. Brown and K. The funders had no role in study design, data collection and interpretation, or the decision to submit work for publication.

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Abstract Whole-genome sequencing WGS of pathogens is becoming increasingly important not only for basic research but also for clinical science and practice. Main Since the publication of the first shotgun-sequenced genome cauliflower mosaic virus 1 , the draft human genome 2 and the first bacterial genomes Haemophilus influenzae 3 and Mycoplasma genitalium 4 , and enabled by the rapidly decreasing cost of high-throughput sequencing 5 , genomics has changed our understanding of human and pathogen biology.

Table 1 Advantages and disadvantages of different viral sequencing methods Full size table. Box 1: RNA-seq and metagenomic diagnostics For cases of encephalitis of unknown origin, metagenomic techniques are promising diagnostic tools. Box 2: Whole-genome sequencing of Zika virus Whole-genome sequencing WGS of Zika virus can help to understand the epidemiology of the recent outbreak in South America, including the origin and spread of the virus, and the connection between the virus and microcephaly.

Why sequence viruses in the clinic? Why sequence whole genomes? Why do we need deep sequencing? Practical considerations Sequencing viral nucleic acids, whether from cultures or directly from clinical specimens, is complicated by the presence of contaminating host DNA Table 2 Limitations of viral sequencing compared with bacterial sequencing Full size table. Figure 1: Methods for sequencing viral genomes from clinical specimens.

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