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Nature Reviews Microbiology 6, 260–261 (1 April 2008) | doi:10.1038/nrmicro1881

Genomic 'valleys of death'

Stephen Bentley

Random fragments are cloned into plasmid vectors before being introduced into Escherichia coli by transformation to be replicated in preparation for DNA sequencing. Although the cloning process is essentially random, the resulting assembled sequences have an uneven distribution across the sequenced genome, with some regions having no clone coverage (Fig.