The current GATK version is 3.7-0
Examples: Monday, today, last week, Mar 26, 3/26/04

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Get notifications!

You can opt in to receive email notifications, for example when your questions get answered or when there are new announcements, by following the instructions given here.

Got a problem?

1. Search using the upper-right search box, e.g. using the error message.
2. Try the latest version of tools.
3. Include tool and Java versions.
4. Tell us whether you are following GATK Best Practices.
5. Include relevant details, e.g. platform, DNA- or RNA-Seq, WES (+capture kit) or WGS (PCR-free or PCR+), paired- or single-end, read length, expected average coverage, somatic data, etc.
6. For tool errors, include the error stacktrace as well as the exact command.
7. For format issues, include the result of running ValidateSamFile for BAMs or ValidateVariants for VCFs.
8. For weird results, include an illustrative example, e.g. attach IGV screenshots according to Article#5484.
9. For a seeming variant that is uncalled, include results of following Article#1235.

Did we ask for a bug report?

Then follow instructions in Article#1894.

Formatting tip!

Wrap blocks of code, error messages and BAM/VCF snippets--especially content with hashes (#)--with lines with three backticks ( ``` ) each to make a code block as demonstrated here.

Jump to another community
Picard 2.10.2 is now available at
GATK version 4.beta.2 (i.e. the second beta release) is out. See the GATK4 BETA page for download and details.

Local realignment output issue

cwardellcwardell Tokyo, JapanMember


I've followed the suggested protocol for local realignment - first using RealignerTargetCreator and then IndelRealigner, but have unexpected results.

Let's call the two BAMs I'm realigning "normal" and "tumour" or N and T for short. Once realigned, I've split the resulting NT BAM file (using readgroup tags, although I see from the docs that it can create separate files natively) back into the original N and T BAM files and discovered something odd. I was expecting the pre-realignment N and T files to contain the same number of reads as the post-realignment files, only the coordinates that reads are mapped to would be different.

However, I notice that post-realignment files contain significantly fewer reads because unaligned reads and reads not aligned to the autosomes or sex chromosomes have been removed. However, these reads alone do not account for the difference; large numbers of reads aligned to the 24 chromosomes are now missing.

Can you tell me more about the reads that are removed? I suspect it to be an alignment quality issue, but cannot find direct reference to this behaviour in the documentation. I'm currently keeping both my pre and post-realignment bam files, but ultimately there will be space constraints and I'll have to choose and would like to make the most informed decision possible.


Best Answers


  • cwardellcwardell Tokyo, JapanMember

    Very astute. Yes I did; I had assumed that specifying windows to realign within would simply make the process faster by only realigning within those regions, but I think you're suggesting that all the data not within those regions is discarded. Am I correct? This resolves the issue, unless in a future update you'd be so kind as to add a flag to realign within windows but not discard the rest of the data.

    Thanks for you help.

  • cwardellcwardell Tokyo, JapanMember

    As ever, thanks for your input - problems solved, things running smoothly again.

Sign In or Register to comment.