contig N99 length QC threshold 2000 Damion Dooley Assembly QC The contig N99 length QC threshold is the minimum length that a contig N99 or NG99 length datum can be for satisfactory QC. This threshold avoids having too many gene coding regions prematurely clipped inside short contigs. An assembly having 1% or more of its content in less than 2Kbp chunks is cause for concern. Bacterial genes are generally about 1Kbp in length. contig length requires discussion