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Malaysian Journal of Medical Sciences
School of Medical Sciences, Universiti Sains Malaysia
ISSN: 1394-195X
Vol. 25, No. 2, 2018, pp. 20-26
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Bioline Code: mj18018
Full paper language: English
Document type: Review Article
Document available free of charge
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Malaysian Journal of Medical Sciences, Vol. 25, No. 2, 2018, pp. 20-26
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Overlooked: Extrachromosomal DNA and Their Possible Impact on Whole Genome Sequencing
Dennin, Reinhard H
Abstract
Extrachromosomal (ec) DNA in eukaryotic cells has been known for decades. The
structures described range from linear double stranded (ds) DNA to circular dsDNA, distinct from
mitochondrial (mt) DNA. The sizes of circular forms are described from some hundred base pairs
(bp) up to more than 150 kbp. The number of molecules per cell ranges from several hundred to a
thousand. Semi-quantitative determinations of circular dsDNA show proportions as high as several
percentages of the total DNA per cell. These ecDNA fractions harbor sequences that are known to
be present in chromosomal DNA (chrDNA) too. Sequencing projects on, for example the human
genome, have to take into account the ecDNA sequences which are simultaneously ascertained;
corrections cannot be performed retrospectively. Concerning the results of sequencings derived
from extracted whole DNA: if the ecDNA fractions contained therein are not taken into account,
erroneous conclusions at the chromosomal level may result.
Keywords
extrachromosomal; episomal; genome; sequencing; chromosome
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