Fig. 4From: AfterQC: automatic filtering, trimming, error removing and quality control for fastq dataAn example of how automatic trimming works. Data is obtained from a cell-free DNA quality control sample, and sequenced by Illumina NextSeq 500 sequencer. a is the base content percentage curve before trimming and filtering, from which we can find base contents change dramatically in front and tail; b is the curve after trimming and filtering, from which we can find that the bad cycles in the tail are all trimmed, while only part of the front is trimmed. This results from the fact that we use different thresholds for the front and tail, since unflatness in front is more probably caused by different fragmentation methods, while unflatness in tail is usually caused by lab preparation or sequencing artefactsBack to article page