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What is chr EBV in human sam file?

I noticed that the header of SAM files resulting from a Bowtie2 besides having the human chromossomes (1-22+x+y+M), also have a EBV chromossome. What is it? Should I be worried?

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sam bowtie2

Epstein-Barr-Virus decoy sequence. Plenty of information on that available via a simple google search ;-D

1 answer

That is Epstein-Barr Virus (human herpes virus genome). Human decoy genome which is what you must have aligned to, has that sequence incorporated in it.

Don't think so cause these are the names of bowtie2 index files: GCA_000001405.15_GRCh38_no_alt_analysis_set.fna.bowtie_index.1.bt2 GCA_000001405.15_GRCh38_no_alt_analysis_set.fna.bowtie_index.2.bt2 GCA_000001405.15_GRCh38_no_alt_analysis_set.fna.bowtie_index.3.bt2 GCA_000001405.15_GRCh38_no_alt_analysis_set.fna.bowtie_index.4.bt2 GCA_000001405.15_GRCh38_no_alt_analysis_set.fna.bowtie_index.rev.1.bt2 GCA_000001405.15_GRCh38_no_alt_analysis_set.fna.bowtie_index.rev.2.bt2 GCA_000001405.15_GRCh38_no_alt_analysis_set.fna.bowtie_index.tar.gz

They have GRCh38, which means they're human. Besides SAM headers have all human chromossomes 1 to 22, X, Y, Mitochondrial, chrUn and then this chr EBV

Oh i'm sorry, now understand what you mean. It's a decoy, so it's basically normal

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