Hi, when I used the DupliFrame function to copy each frame of double-helix, the first structur doesn’t show up, rather some arrows indicating tis place comes up. Here’s a picture:
Weird, I’ve never seen that. I’ve also never seen a Mesh set to Wire draw in Solid. Could you post the file?
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Where can I upload the file? Can I e-mail it to you?
>>Edit
nevermind, I got it.
You are dupliframing the empty and not the tube.
Click on the Empty, deselect Dupliframes, click on the Tube and select Dupliframes 
Edit: You should check out the Array modifier, it’s much more convenient for symmetric structures.
awesome! thanks a lot!