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. Author manuscript; available in PMC: 2023 Mar 1.
Published in final edited form as: Small Methods. 2022 Jan 22;6(3):e2101251. doi: 10.1002/smtd.202101251

Figure 5. FASTQ file elements.

Figure 5.

(1) Sequence identifier: starts with the symbol “@” followed by the necessary information for troubleshooting and demultiplexing: identification of the instrument, flow cell, lane, tile, coordinate information of the cluster within the title, the read number as a member of a pair (1 or 2), and the filter indication (Y indicates the read is filtered, while N is otherwise). (2) Sequence: base calls. (3) Quality score identifier line: this is the separator and is always a plus (+) sign. (4) Quality score: base call quality (Phred +33) encoded by ASCII characters representing numerical quality scores for the raw sequence in line 2. The meaning of the quality value characters is found at https://ascii.cl/.