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Is the Run Id information, in fastq file headers, sequential?

Is the run number, that is present as the second field in fastq file header, sequential? What I mean if there are two run numbers in two different fastq files with the same Instrument ID, x and y. If x < y, does this imply that experiment with run number x is done before experiment y?

For example, consider these two headers:

1) @EAS139:76:FC706VJ:6:1101:20273:23294 1:N:0:CGATGT

2) @EAS139:89:FC706VJ:7:1101:7912:1314 2:N:0:GTGAAA

Can I say, that the experiment in 1st fastq file (run number 76) was done before the experiment associated with the 2nd fastq file (run number 89)?

rna-seq chip-seq rna-seq sequencing next-gen

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1 answer

Yes the number in second location should be a cumulative run ID for that sequencer. Assuming it has not been altered. Sequence in your run example 1 was run before example 2. You can't be sure the experiment was done before though.

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