Hi everyone, I am new in the field of bioinformatics. I have generated RNA Seq data, my sequencing was run on NextSeq with single end reads. I have 4 fastq files per sample and therefore need to combine these 4 files into one file. I have used the cat command in linux to combine these four files into one. But when, I am using the combined file for mapping it is throwing the error. (showing that file is not in proper fastq format for mapping). Does anyone has experience on combing these file and using them for mapping?. Or can I map these files separately.