Cos ends in cosmids

Richard Near rocket1 at
Sun Apr 10 19:27:23 EST 1994

I am posting this question for a friend who is having 
difficulties with his cosmid:

Dear Rich,

        Do you know off hand how much sequence in the vicinity of the
Coehesive ends of lambda are needed for packaging functions to be carried
out.  Apparently the proteins that package lambda do not bind directly on
the Cos sites.  The reason I ask is because I'm trying to  clean up a
cosmid, which has been giving me problems.  It turns out that the cosmid
contains an E.Coli IS-1 element that is responsible for a high frequency
of deletions and rearrangements.  To remove it I must cleave with PvuII,
which has a site about 200 bp from the coehesive end.

Thanks Larry

If you have any advice please either post it here or send it to
me via email

rocket1 at

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