Silent ClaI sites - info ?

vernon VERNON at
Thu Sep 23 08:02:38 EST 1993

In article <jjw-230993123321 at>, jjw at (Jeremy Weinman) writes:
>Silent ClaI sites
>Does anybody out there in netland know of any info (published or otherwise)
>on why ClaI sometimes doesn't recognize a ClaI site?  We've got some clones
>which we have been mapping and we have a cla site that cuts on the basis of
>some unknown or perhaps archane variable, seemingly regardless of how well
>other cla sites in the clone are cutting.  Any thoughts?
>Dr. Jeremy Weinman                              Email:
>jjw at
>Plant Microbe Interaction Group                 Phone:  61 6 2495051
>Research School of Biological Sciences          Fax:    61 6 2490754
>Australian National University                  Snail:  PO Box 475,
>                                                        ACT 2601, AUSTRALIA

When a dam methylation site (GATC) overlaps a ClaI site, then
the site will not cut, unless your DNA was prepared from a dam- E.coli
(Not cut actually means cuts poorly or not at all depending upon the
DNA prep, probably due to how completely sites were methylated)

 Michael Benedik                INTERNET: Benedik at
 Dept. of Biochemical & Biophysical Sciences
 University of Houston              BITNET: Benedik at uhou

Does this apply exclusively to ClaI sites, or is there a list of
additional restriction enzymes which act in an analogous way?

| Dr. Vernon E. Coyne,                                               |
| Microbiology Department,            Tel: (27-21) 650-3259/70       |
| University of Cape Town,            Fax: (27-21) 650-4023          |
| Private Bag,                        E-mail: vernon at |
| Rondebosch, 7700                                                   |
| South Africa                                                       |

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