cutting large circular DNA molecules

[The Duck]

On Tue, 19 Apr 2005 22:31:55 -0700, Bob wrote:

> On Tue, 19 Apr 2005 19:47:19 +0200, The Duck <theduck at earth.com>
> wrote:
> 
>>Dear All,
>>
>>I was hoping that you could give me some advice to the following problem:
>>
>>I would need to cut large circular DNA (several hundreds of kilobases in
>>size) exactly once (or at most only a few times). 
> 
> You hedged there in (). That makes a big difference. Cutting exactly
> once -- without knowing anything -- sounds hard. Cutting "not much"...
> Why not use a rare-cutting restriction enzyme? An enzyme with an
> 8-base recognition sequence cuts, on average, every 65 kb.
> 
> Look at the New England Biolabs catalog. Their discussion of megabase
> mapping may help you.
> 
> bob

Thank you bob, will do.