Reads in FASTQ file produced by CASAVA 1.8 contain 'N' or 'Y' as a part of an idetifier. 'Y' if a read if filtered, 'N' if the read if the read is not filtered. The workflow cleans up the filtered reads.

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If you haven't used the workflow samples in UGENE before, look at the "How to Use Sample Workflows" section of the documentation.