Contents
What does it mean to sort a BAM file?
coordinate sorted
A bam is coordinate sorted if the reads are sorted by coordinates. So reads from the beginning of the first chromosome are first in the file. That’s what samtools sort is for. The opposite would be ‘sorted by name’ in which reads are sorted by their read ID.
Why do BAM files need to be sorted?
In order to efficiently display/access the data the BAM file has to be sorted. Last edited by GenoMax; 10-17-2013 at 02:17 PM. Sorted BAM has the data sorted by chromosomes/contigs/scaffolds whatever is in your reference genome. In order to efficiently display/access the data the BAM file has to be sorted.
How do I compare BAM files?
To compare the BAM files, the genome is partitioned into bins of equal size, then the number of reads found in each bin is counted per file, and finally a summary value is reported. This value can be the ratio of the number of reads per bin, the log2 of the ratio, or the difference.
What is BAM index?
A BAM file (. bam) is the binary version of a SAM file. A SAM file (. sam) is a tab-delimited text file that contains sequence alignment data. Indexing: IGV requires that both SAM and BAM files be sorted by position and indexed, and that the index files follow a specific naming convention.
How much memory does SAMtools sort use?
While running SAMtools, we provisioned only 45 Gb (1.5 Gb for each of the 30 threads) so one should only specify 80-90% of available memory to SAMtools.
How to remove low quality reads from BAM files?
This is a good way to remove low quality reads, or make a BAM file restricted to a single chromosome. We’ll be focusing on just a few of samtools functions in this series of exercises.
How is SAMtools used to view.bam files?
These files are compressed, so they can’t be viewed using standard unix file viewers such as more, less and head. Samtools allows you to manipulate the .bam files – they can be converted into a non-binary format ( SAM format specification here) and can also be ordered and sorted based on the quality of the alignment.
Do you need a Bam alignment file for Bowtie2?
While the SAM alignment file output by Bowtie2 is human readable, we need a BAM alignment file for downstream tools. Therefore, we will use Samtools to convert the file formats. To use samtools we will need to load the module:
Which is output from aligning reads to databases?
… As we showed you yesterday, the main type of output from aligning reads to a databases is a binary alignment file, or BAM file. These files are compressed, so they can’t be viewed using standard unix file viewers such as more, less and head.