Mapping Phred+64 encoded reads with Bowtie2
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3.1 years ago
Denis ▴ 210

Hi, I faced with strange behavior of Bowtie2. I mapped reads with Phred+64 encoding by command:

bowtie2  --very-sensitive -x index -U R1.fastq -S Alignment.sam


I'm wondering why i didn't get any error message in that case? Is Bowtie2 able to determine reads encoding format automatically?

genome alignment software error • 689 views
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You should add --phred64 which indicates that qualities are Phred+64.

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Thanks! But why i didn't get error by using this command line? I use this command a long time and only recently realized that the reads have Phred+64 encoding. How it may influence on the mapping results (everything looked well in resulted SAM file i usually got)?

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If I had to guess, the mapping results might be skewed as bowtie2 might (notice I said might) think that you have just really good higher quality sequences than you actually have. Not sure if bowtie2 can automatically determine the encoding of the reads or not.