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#NGS

3 public questions tagged with this topic.

Sequencing

Which is used to align reads in NGS?

Next-generation sequencing instruments generate tens of millions of short reads that individually are too short for direct biological interpretation. Bioinformatics mapping uses algorithms like BWA, Bowtie2 or Minimap2 to align each read to a reference genome assembly of same species, finding best match position tolerating mismatches and indels. Successful alignment reveals coverage depth, variants and expression levels. Fluorescent scanners capture images, polyacrylamide gels were used for Sanger fragment sizing, pH meters are irrelevant. Reference genome mapping is therefore essential step converting raw reads to genomic coordinates.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Sequencing

Next-generation sequencing allows:

Next-generation sequencing is defined by high-throughput massively parallel architecture that overcame Sanger's one-fragment-at-a-time limitation. Flow cells, bead arrays or semiconductor chips simultaneously sequence millions to billions of clonally amplified library molecules, each generating independent reads in parallel reactions. This parallelism yields gigabases of data per run, enabling whole genome, exome, metagenome and transcriptome analysis cost-effectively and rapidly. Concepts like one gene, low throughput or single template describe only first-generation sequencing. Parallel sequencing capability explains why NGS revolutionized modern genomics dramatically.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Sequencing

In NGS, what is the principle of sequencing-by-synthesis?

Sequencing-by-synthesis is the core principle of Illumina next-generation sequencing. Library fragments immobilized on flow cell are amplified into clusters, then polymerase synthesizes complementary strand stepwise. Each cycle adds fluorescently labeled reversible terminator dNTPs that block further extension until imaging is complete. After color detection identifying base, terminator and fluorophore are chemically cleaved to allow next incorporation. This iterative labeled nucleotide addition contrasts with ligation-based SOLID, hybridization microarrays relying on probe annealing, or pH change detection in Ion Torrent. Hence labeled nucleotide addition defines SBS.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details