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--- mkatari-bioinformatics-august-2013-bowtienotes [2014/04/30 12:24] – created mkatari
+++ mkatari-bioinformatics-august-2013-bowtienotes [2014/07/03 13:19] (current) – mkatari
@@ Line 1: / Line 1: @@
-#Bowtie on Cassava
+[[mkatari-bioinformatics-august-2013|Back to Manny's Bioinformatics Workshop Home]]
-) Download cassava genome from phytozome
+====== Creating a Bowtie Index and Performing an alignment using Cassava as a reference ======
-wget ftp://ftp.jgi-psf.org/pub/compgen/phytozome/v9.0/Mesculenta/assembly/Mesculenta_147.fa.gz
+This is a quick example of how to build a bowtie index and executing bowtie. Normally you will create the index only once you there is no need to create a special script for it. Just make sure you are in **interactive mode** mode and we can do everything on the command line.
-) created a directory called cassava
+Once you have found the sequence on the web you want to use as a reference you can use the linux command wget to download it quickly. And to make sure we keep our data organized, let's create a directory called **cassava** where we will store the file.
-mkdir cassava
-) move fasta sequence in the directory
+So first steps are to create the directory and download the file.
-mv Mesculenta_147.fa.gz cassava/
+<code>
+mkdir ~/cassava
-) uncompress using gunzip
 cd cassava
+wget ftp://ftp.jgi-psf.org/pub/compgen/phytozome/v9.0/Mesculenta/assembly/Mesculenta_147.fa.gz
+</code>
+Now we will uncompress the file using gunzip
+<code>
 gunzip Meculenta_147.fa.gz
+</code>
-) Count number of scaffold in the file
+To see how many scaffolds we in our file we can **grep** for the greater-than sign and then using the command **wc** to count lines.
-grep ">" Mesculenta_147.fa | wc
-) load bowtie module
+<code>
+grep ">" Mesculenta_147.fa | wc -l
+</code>
+In order to use Bowtie2 commands we have to first load the module
+<code>
 module load bowtie2
+</code>
+In order to create the index, which will be used like a database when we are aligning the reads to the reference, we use the command bowtie2-build. For cassava this should take about 10 minutes.
-) Create the bowtie index.
+<code>
 bowtie2-build Mesculenta_147.fa cassava
+</code>
-) Run Bowtie using single end fastq as input. See bowtie2 for instructions on how to run it on pair-end sequences.
+Based on the the type of sequences you have ( single end or pair end ) the options to run bowtie are slightly different. To run single end reads use -U followed by the file name. If it is pair-end then use -1 first file -2 second file.
+See the link for [[http://bowtie-bio.sourceforge.net/bowtie2/manual.shtml|bowtie2]] for more detailed options and arguments that bowtie2 accepts.
+<code>
 bowtie2 -x cassava/cassava -U test.fastq -S test.sam
+</code>