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Essay On Human Genome Sequencing

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1. Current challenges in human genome sequencing

Technologies in sequencing are highly accurate but have limitations in read-depth and read length. Read-depth refers to sequencing the highly repetitive regions of DNA with few to no errors. Illumina HiSeq and PacBio have allowed geneticists to fill in the gaps of the human genome saving time and money. In the scope of the read depth issue, researchers are still having issues with undetectable structural variants (SV) including copy number variants (CNV) and small nucleotide polymorphisms (SNP). (Bickhart, et al. 2017).
Illumina HiSeq is one of the more accurate forms of DNA sequencing technology, about 99% accurate. The newest version of HiSeq is TruSeq nano and NEBNext Ultra. Sequencing …show more content…

New approaches to sequencing include Illumina, PacBio SMRT Chip technology and the nanopore minION. Illumina is accurate about 99.9% of the time. PacBio is by far the most accurate of the three sequencing technologies. Although the nanopore minION is not as accurate as PacBio SMRT and Illumina, this technology is able to detect anomalies in the genome. All of these sequencing technologies have a cost associated with them, but the Oxford Nanopore minION is the most expensive.
Illumina is a less expensive way to sequence. At 99.9% accuracy, Illumina is able to provide short read lengths to be analyzed using Phred. Phred is a base calling algorithm that calculates the location of a fluorescent peak and records the base for that particular fluorescent label. This technology is not ideal due to portability and sequencing prep. The DNA still has to be amplified to create a cDNA library using bridge amplification. Illumina requires a polymerase and fluorescently labeled dideoxynucleotide triphosphates (ddNTPs) followed by Sequencing by synthesis (SBS). This is the final step in generating the wavelength reading of nucleotide bases. (White, et al. 2016)
The Oxford Nanopore minION sequencer is able to produce reads up to 300kb. Unlike Illumina and PacBio, Nanopore technology can detect structural variants and cytosine modifications including hydroxymethylcytosine, formylcytosine and methylcytosine. The purpose of this

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