Blunt-end cloning

[Dickens Lum]

Hi all..



       I've performed blunt-end cloning of PCR products (size 200, 500

and 1000 bp)using Stratagene PCR-Script Cloning kit. The result was not

very good and I only got 5 ~ 10 white colonies in each clone. However,

the real problem now is that the extracted plasmid is extremely resist

to restriction digest. Some of the sites never cut. Can anybody

help..??? Any other methods to confirm the present of clones..???

Besides, do I need to linearize the plasmid before PCR it..??



Any suggestion and discussion are welcome. Thanks!



Regards,

Dickens