Skip the Dnase I treatment, you can extract RNA with DNA. In another word, replace the Dnase I with RNaseA, you can get the DNA.

Thanks Jincheng for your answer.

But I'm extracting both RNA and DNA, I first run the lysate through a DNA column and then the flowthrough through an RNA column. I can retrieve the RNA, but no DNA is binding to the DNA column.

I use Qiagen kits (all prep kit)

• I'm guessing the DNA is not being eluted from the column in your flow through
• Have you checked that you can see DNA in the flow through (on an agarose gel) ?
• I am slightly suspicious of the way you describe extraction
• Send me your SOP and then I can better appraise your method and make suggestions