Hi,

A read group is a set of reads generated from a single run of sequencing instrument.

For instance, if a single library preparation from one biological sample which is run on a single lane Of a flow cell ,all the reads from that lane belongs to the same read group.

If multiplexing is involved,then each subset or subgroup of reads that arise from separate library will run on that lane and constitute separate read groups.

Additionally, if a single sample has several read groups then it should be made sure whether the DNA libraries are distinct Or same..if that's distinct then read groups are not duplicate.

technically the previous answer is correct of course. I would add that depending on the context it can also be a group of samples that share a particular feature. For example if you want to discover SNPs between two varieties of a cultivated plant, you may want to group all samples (biological replicates) from each given variety altogether and call the SNPs between the groups (RG). See the forum section at seqanswers.com if our answers are not precise enough.

Many thanks Aishwarya and Jean-François for your replies. I have downloaded a WES data-set containing 21 tumor samples from SRA. Now there is two questions?

1. There was no information about library for any sample after exploring sam/bam files, hence I cannot determine whether the DNA libraries are distinct or same? Is there any way to find it?

2. Authors of this data-set reported that they also provided WES on normal matched germline DNA from blood for each sample. But I cannot find these WES data? Is it possible that authors merged tumoral WES and normal WES data (as a read group) for each sample? @