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  • bre
    Member
    • Dec 2009
    • 11

    #1

    Building indexes with bowtie-build

    Hello, I am currently trying to align two closely related genomes from multiple sequence fasta files. I have a target genome which is made of 1168 sequences in a single fasta file and I wish to use this to build indexes. Initially I did this with the command "bowtie-build target_file.fa t_index". This ran in a reasonable amount of time and produced 6 index files: t_index.1.ebwt, t_index.2.ebwt, t_index.3.ebwt, t_index.4.ebwt, t_index.rev.1.ebwt, t_index.rev.2.ebwt.
    I then ran the command "bowtie t_index -f -t -p4 -l 13 ../PATH/TO/QUERY output.map" to run an alignment, where QUERY is also a multiple sequence fasta file where each sequence length is <= 1024 bases. My output was not what I was expecting; I got only 5.03% alignment when I was expecting over 90%. This lead my to wonder whether or not indexes had been created correctly. Is bowtie-build able to take a multisequence fasta file? Maybe each index file was being overwritten by each following sequence in the target file? I tweaked some parameters and was still not able to get over 6% alignment.
  • bre
    Member
    • Dec 2009
    • 11

    #2
    Self alignment

    I tested the indexes by running them against the sequences they were created from and only got 67% alignment so this leads me to further doubt the indexes obtained. Has anyone else had similar problems?

    Comment

    • Xi Wang
      Senior Member
      • Oct 2009
      • 317

      #3
      I have successfully built the index from multiple sequences in a fasta file and the mapping results seem all right. I guess the problem you encountered is because of the length of the sequence you queried. Such kind of NGS mapping tools is mainly designed for short read alignment.
      Xi Wang

      Comment

      • ZZQ
        Junior Member
        • Mar 2010
        • 3

        #4
        I've heard of bowtie, but have not a try yet.

        Comment

        • sperry
          Junior Member
          • Feb 2010
          • 7

          #5
          For the read lengths you are working with, you are probably better off using a different alignment tool. BWA has an alignment option that specifically accommodates longer read lengths (bwasw). http://bio-bwa.sourceforge.net/

          Originally posted by bre View Post
          I tested the indexes by running them against the sequences they were created from and only got 67% alignment so this leads me to further doubt the indexes obtained. Has anyone else had similar problems?

          Comment

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