Genomic DNA preparation

[Jongrak Kittiworakarn]

Dear all
        I have extracted genomic DNA from mosquito larvae.   I am trying
to obtain high quality genomic DNA in reasonably large pieces of about
100 kb to construct a library. I am therefore concerned about the
shearing forces during centrifugation of the DNA. Is this a real
concern?  How many g's can I safely use (and for how long) for a
centrifugation step?  Is using chloroform only to extract protein good
enough or should I also use phenol?

sincerely,