DESCRIPTION

These set of scripts is designed to align multiple samples of same species to a reference genome, do preprocessing, and then call variants. The scripts use the following software for given purposes in the given order.

1. trimgalore to trim adapters, clip the ends of the reads and generating fastqc reports
2. bwa mem for aligning
3. samtools sort -n for sorting by name
4. samtools fixmate for fixing mate information
5. samtools sort for sorting by coordinates
6. samtools markdup for marking duplicates
7. picard-tools AddOrReplaceReadGroups for addding and replacing RGtags
8. picard-tools CleanSam for setting Mapping Quality 0 for the sequences that are not aligned.
9. samtools index for indexing
10. samtools coverage for coverage reports
11. bamtools stats for alignment reports
12. bcftools for variant calling

USAGE

Download

git clone https://github.com/evolozzy/NGS-Pipeline.git

Before using

• Make a subdirectory named Data in the folder containing your scripts and copy your files there, or change the line containing DATASOURCE in your PARAMETERS file, and set it to the folder that contains your data.
• If you have two or more sets of reads to merge keep them in separate directories in Data directory.
• Make sure you have your reference file.
• Edit RGTAGS file carefully, the files belonging the same sample should have the same SM (sample name).

Using

Setting the parameters

• Carefully change the PARAMETERS.
  • Set the REFERENCEFILE to the path to reference.
  • If you are running on multiple threads set THREADS to number of cores you want to use.
• Set the directories to be used in DIRECTORIES file.
  • If you're not running the scripts in the directory you have the scripts change the line containing WD to the path that contains your scripts.
• Install required software, and set PROGRAMPATHS.

Running

Inside the folder:

./runall.sh 

Or outside the folder:

/path/to/scripts/runall.sh

If you encounter any errors during the process and clean all the files created by the script:

./resetanalysis.sh

Best Practices

• Before running runall.sh, use trimall.sh to quality control the trimming process. Checkout the fastqc reports after trimming and set PARAMETERS accordingly.
• Make sure that the core numbers are set properly. Try to use parallel more, but it depends on the number of files. For low numbers of files

How does this set of scripts work?

0. The script checks
   • if the files are in place
   • if the software is installed
   • calculates a good way to use the cores available
   • builds references from reference file
1. Trimming is done with trimgalore.
2. Aligning is done with bwa
3. Preprocessing is done with samtools and picard-tools.
   1. First, the files are sorted by name and mate info is fixed.
   2. Second, the files are sorted by coordinate and duplicates are marked.
   3. Third, the files are cleaned from reads that were not aligned.
   4. Last, RG tags are added.
4. Variants are called with bcftools.

• The middle files can be kept, deleted, or archived to another location.
• The code also generates reports of trimming (fastqc reports), alignment, and coverage.