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Introduction to DNA Sequencing

intro to NGS sequencing
caricature of the DNA sequencing with the DNA helix coming into the computer producing reads on the screen
DNA Sequencing is the process of reading the nucleotides present in DNA: determining the precise order of nucleotides within a DNA molecule

DNA Sequencing generally refers today to any Next Generation Sequencing (NGS) technology that is used to determine the order of the four bases (A, T, C, G) in a strand of DNA. NGS has overtaken Sanger sequencing especially for large-scale genome projects. The course therefore focuses more on NGS methods that have been described below.

Advantages of NGS over classical Sanger sequencing

NGS holds two distinct advantages over Sanger sequencing in terms of speed.

Firstly, NGS enables the combination of chemical reactions and signal detection, whereas Sanger sequencing treats these processes separately. Additionally, NGS achieves massive parallelism, allowing for multiple reads to be taken simultaneously, which is not possible in Sanger sequencing.

Although the initial human genome sequence cost around $300 million back in 2001, sequencing costs have reduced significantly since then. NGS technology, particularly with Illumina sequencing, has brought the cost closer to the expected $1,000 mark. NGS also requires significantly less starting DNA/RNA compared with Sanger sequencing. Furthermore, NGS offers increased accuracy due to more repeated readings, resulting in higher coverage, enhanced precision, and greater sequence reliability. However, individual reads in NGS may be less accurate compared to Sanger sequencing, but the overall advantages in terms of speed, cost, sample size, and accuracy make NGS an invaluable tool in modern genomics research and applications.

Please check some of the attached resources for more detailed information on the Next generation Sequencing.

© Wellcome Connecting Science
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Bioinformatics for Biologists: Analysing and Interpreting Genomics Datasets

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