Shearing genomic DNA

[Paul N Hengen]

Keith Grimaldi (regokag at ucl.ac.uk) wrote:

> I need to lightly shear a lot of genomic DNA samples - does anybody 
> have any good ways to do this?

I just did it for E. coli genomic DNA isolated using the Qiagen protocol I got
off the net. After isolation I passed it through an 18G needle about 10 times,
but it was still as > 10 kb fragments. Since I wanted to make a library with
0.5-6 kb fragments in the vector, I sonicated it using a Branson sonicator
model 450 set at 1 unit of output power and 50 pulses per minute. With a 200 to
500 ul sample of DNA in an eppendorf tube, I found that pulsing for 15-20 times
gave the optimal fragment sizes that I want - a smear of DNA on an agarose gel
was in the correct range.

--
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* Paul N. Hengen, Ph.D.                           /--------------------------/*
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