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<title>Per Base N Content</title>
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<style type="text/css">
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font-family: sans-serif;
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<h1>Per Base N Content</h1>
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If a sequencer is unable to make a base call with sufficient confidence
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then it will normally substitute an N rather than a conventional base]
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This module plots out the percentage of base calls at each position for
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which an N was called.
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<p><img src="per_base_n_content.png"></p>
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It's not unusual to see a very low proportion of Ns appearing in a sequence,
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especially nearer the end of a sequence. However, if this proportion rises
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above a few percent it suggests that the analysis pipeline was unable to
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interpret the data well enough to make valid base calls.
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This module raises a warning if any position shows an N content of >5%.
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This module will raise an error if any position shows an N content of >20%.