Page Comparison

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Using bwa mem for RNA-seq alignment is sort of a "poor man's" RNA-seq alignment method. Real splice-aware aligners like tophat2STAR, hisat2 or STAR tophat have more complex algorithms (as shown below) – and take a lot more time!

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BWA MEM does not know about the exon structure of the genome. But it can align different sub-sections of a read to two different locations, producing two alignment records from one input read (one . One of the two will be marked as secondary (0x100 flag).

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# Make sure you're in an idev session
idev -m 120 -N 1 -A OTH21164 -r CoreNGS-Thu      # or -A TRA23004
# or
idev -m 90 -N 1 -A OTH21164 -p development   # or -A TRA23004

# Load the modules we'll need
module load biocontainers
module load bwa
module load samtools

# Copy over the FASTQ data if needed
mkdir -p $SCRATCH/core_ngs/alignment/fastq
cp $CORENGS/alignment/*.gz $SCRATCH/core_ngs/alignment/fastq/

# Make a new alignment directory for running these scripts
cds
mkdir -p core_ngs/alignment/bwamem
cd core_ngs/alignment/bwamem
ln -sf ../fastq
ln -sf /work/projects/BioITeam/ref_genome/bwa/bwtsw/hg38

Now take a look at bwa mem usage (type bwa mem with no arguments, or bwa mem 2>&1 | more). The most important parameters are the following:

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