short dsDNA

[Luke]

Hello Guys

I need your help, once again... For an experiment I need dsDNS on the length between 20bp and 100bp. The sequence of the base isn`t important, but all the Fragments must have the same sequence. Any idea where I can get this for a low price? 

Thanks a lot for help

Luke

[Koeng]

Synthesize primers (purified if you need it to be clean) and anneal them to each other. (Do that step yourself, they charge you a limb for them to do it)

If you need <40bp, get it from invitrogens value oligo program. If you need them longer and more of them, https://www.idtdna.com/pages/products/dna-rna/96-and-384-well-plates is reasonable buy.

-Keoni

[Simon Quellen Field]

It would seem to someone like me (who has never done this) that you could take any DNA, cut it up, run it through an electrophoresis gel, select a tiny part of a band, and put that into your thermocycler, and repeat until you get a single band.

Proving that they all have the same sequence I expect would be harder.

:-)

Always looking for the "pure" DIYBio approach, just for kicks.

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[Cory Tobin]

One method would be what Keoni suggested: buy two different ssDNA
oligos with complementary sequences, mix them together, heat to ~95C
for a bit and then cool. This will work well if your target length is
less than 60 bases. When you go past 60 bases the price per base goes
up significantly. You could also request they PAGE purify the oligos
which would give you a narrower distribution of lengths.

Another option is to use PCR to amplify a region of a template DNA
molecule that is exactly the length that you need. This will give you
a large amount of DNA for cheap. I'm not sure how accurate this is
relative to annealing ss oligos.

Or do what Simon suggested and cut a plasmid with a blunt-cutting
restriction enzyme. Assuming you have a plasmid with restriction
sites correctly spaced, this will give you the most DNA for your
dollar. But you'll need to gel purify which is laborious if you're
handling a large amount of DNA.

It really depends on how much DNA you need and how much precision is
required. What percent of molecules must be the right length? 99?
99.9?

-cory

[Luke]

Thanks for the great ideas, how you suggest,  I`ve let synthesis some primers. They are complementary to the oligo (dt) Primer. So I can produce with the cheap oligo (dt) primer a lot of the same dsDNA. 

Thanks a lot guys 

Luke