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  • mcek
    Junior Member
    • Nov 2011
    • 1

    #1

    Bowtie - only 4.12% reads aligned to transcriptome

    I'm new to this, so excuse me if it's a stupid mistake I'm making. What I'm really after is expression values for each transcript in a wild-type HEK 293.

    I have found SRS211675 in NCBI Sequence Read Archive, downloaded the SRA file, and converted it to .fastq with fastq-dump.

    Then I have build the bowtie index of the human transcriptome with:

    bowtie-build Homo_sapiens.NCBI36.54.cdna.all.fa homo_sapiens

    Then run bowtie:

    bowtie -p 4 --sam --best homo_sapiens SRR248532.fastq aligned.sam

    I get about 50 'skipped read' warnings and the summary is:

    # reads processed: 20954439
    # reads with at least one reported alignment: 862675 (4.12%)
    # reads that failed to align: 20091764 (95.88%)
    Reported 862675 alignments to 1 output stream(s)

    It seems that cannot be normal. Where am I going wrong here?

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