Ordering DNA of a specific length - (Feb/05/2008 )

Does anyone know where I can order DNA which is 200bps in length? I need it to use as a positive control for some stuff I'm doing and it would be easier to order it like that, and more standardized, than designing and ordering primers and amplifying it myself.

Thanks.

well I don't know of any company that sells primers that long. But I have heard of company that make genes to order... 0.66p per base. But it does look a little expensive for the purpose in mind. (I'll pull out that advet from my junk box if you want to look at it)

It will be much cheaper to amplify.

Exactly. Choose your favorite common template whose sequence you know, like pUC19, and two primers whose 5' ends are exactly 200 bp apart, then amplify the template.

I once needed to make a sequence that was novel and around 200bp long.
What I did was ordered two oligos of around 100bp each with over lapping complimentary ends and two primers for the other ends of these 100bp stretches.
I then used Hot-start PCR to anneal the two 100bp stretches and extend the sequence. I then added the primers and extra taq at cycle 2 and let that amplify the newly created 200bp sequence.

A wee bit of technical footering but once you've got what you want, in principle, down on paper then the rest is just making it work. You need to be at least a little green fingered in the lab to make this work, though.

But the salient issue for this was that it was a novel sequence I needed to create.