Question: Double Peaks For Both Forward And Reverse Tags In Macs2 Model Of Chip-Seq Data - Shall I Be Concerned?
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gravatar for Nick
4.7 years ago by
Nick250
Spain
Nick250 wrote:

I analysed 3 chip-seq replicates (each with its own input control) using macs2. For two of the samples the model produced by macs2 looked fine. I am pasting an example below:

normal macs model

For one of the samples the model graph for both the forward and the reverse tags seems to exhibit double peaks:

weird macs model

This normally happens if you mix libraries of different fragment sizes but this is not the case. Shall I be concerned? What would you do?

chip-seq • 2.2k views
ADD COMMENTlink modified 4.7 years ago • written 4.7 years ago by Nick250

Could you clarify a few things. When you say replicates, are you referring to the same cell type/tissue IP'd using the same antibody? If so, does one such technical/biological replicate give double peaks while another sample presumed to be identical give single peaks? Or, are the double peaks generated by some biologically relevant aspect of the experiment i.e. antibody, condition, etc? Also, lastly, are you seeing these double peaks in an input/control sample as well as an experimental replicate?

The point of these questions is to try to ascertain whether the double peaks are potentially caused by some biology, or by some technical issue.

Bede

ADD REPLYlink written 4.7 years ago by bede.portz470
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