Posts in the 'Bowtie2' category

Bowtie 2 is an ultrafast and memory-efficient tool for aligning sequencing reads to long reference sequences. It is particularly good at aligning reads of about 50 up to 100s or 1,000s of characters, and particularly good at aligning to relatively long (e.g. mammalian) genomes.

Illumina Patterned Flow Cells Generate Duplicated Sequences

The latest Illumina sequencers – such as the HiSeq X, HiSeq 3000 and HiSeq 4000 – use patterned flow cells to enable the discrimination between much more densely packed DNA clusters. While such technology substantially increases the number of reads generated per sequence run, this innovation may lead to an increased number of duplicates, thereby negating the improved yield and making subsequent data analysis potentially more difficult. Further investigation shows that these putative sequencing duplicates are generally in close two-dimensional proximity on a flow cell, which may provide an opportunity to develop bioinformatics solutions to identify and discard such artefacts.

March 2, 2017 HiSeq, All Applications, Bowtie2, HiCUP, Picard

Soft-clipping of reads may add potentially unwanted alignments to repetitive regions

Soft-clipping of sequencing reads allows the masking of portions of the reads that do not align to the genome from end to end, which may be desirable for certain types of analysis (e.g. detection of structural variants). For standard alignment processes soft-clipping may however incorrectly trim reads and lead to the mis-assignments of reads primarily to repetitive regions. This phenomenon appears to vary in severity for different sequencing applications with Bisulfite sequencing being worst off.

May 16, 2016 All Applications, Bismark, Bowtie2, bwa-meth, HISAT2, SeqMonk, Trim Galore!