I did double digestion overnight,purify and used T4 DNA ligase,incubate overnight again and proceed to transformation the following day having used ratio 1:3 Vector:insert.However few colonies were recovered after 16hours with no insert when I confirmed via colony PCR
I know that it is popular to do colony PCR but I recommend a classical restriction analysis. You will get more information from your gel.
I guess that you visualized an aliquot of the vector and of the insert on a gel and that your competent cells have been used before. For ligation I would recommend 16 degres or RT. The most likely problem is the quality of the vector. Check linearization with enzyme one before digestion with the second enzyme. In your specific case, you may consider using Acc65I instead of KpnI. It cuts the same sequence but generates a 5'overhang and is in my hands the more robust enzyme.
I agree with Uwe. Besides that, check your competent cells as competency is lost in many cases due to overtime and inefficient storage. First confirm it by blue white screening if every thing is alright then there is the problem in ligation. Vary the ligation conditions i.e vector insert ratio, duration (longer), and also make sure that your insert DNA is restricted properly (vary the conditions too)
Thanks to all.I changed the ratio to 1:10 as suggested and also added PEG solution 5% hopefully i can get a good result.Thanks once again
Special thanks.I got my ligation successful this time using ratio 1:10 Vector:insert
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