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  • bwa alignment failed

    Hello, I am trying to align my Illumina hiseq data using bwa:

    ./bwa index -c -a bwtsw -p hg19 hg19.fa

    ./bwa aln -t 4 -c hg19 quatrim.fq > quatrim.sai

    ./bwa samse -f quatrim.sam hg19 quatrim.sai quatrim.fq

    Then .sam was convered to .bam

    I used samstool to check the alignment:

    ./samtools idxstats quatrim.bam

    chr1 249250621 1 0
    chr2 243199373 0 0
    chr3 198022430 2 0
    chr4 191154276 1 0
    chr5 180915260 1 0
    chr6 171115067 0 0
    chr7 159138663 0 0
    chr8 146364022 1 0
    chr9 141213431 0 0
    chr10 135534747 0 0
    chr11 135006516 1 0
    chr12 133851895 0 0
    chr13 115169878 0 0
    chr14 107349540 1 0
    chr15 102531392 0 0
    chr16 90354753 0 0
    chr17 81195210 0 0
    chr18 78077248 0 0
    chr19 59128983 3 0
    chr20 63025520 1 0
    chr21 48129895 0 0
    chr22 51304566 0 0
    chrX 155270560 0 0
    chrY 59373566 0 0
    chrM 16571 0 0
    * 0 0 3081338

    When I ran the above steps, everything looked fine. The quality scores of the reads are also very good. I blasted some, and they mapped perfectly to the genome. I am wondering which step(s) might have problems. Thanks!

  • #2
    bwa aln -c is for colorspace data (i.e. from SOLiD platforms). As is bwa index -c

    You state you have Illumina data.

    I suggest removing the -c options from both commands.

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