You are probably having a small amount of uncut plasmid carried over, that will also transform really well. Still, it should work just fine as a cloning strategy.

You can try increasing the digestion time (at least 3 hours, overnight can be better).

Hello,

as it was suggested to you by Amy Klocko, perhaps it is not a self-ligation but rather a non-opening of your vector or at least some of your vectors.

Like the DNA you want to insert and large enough, even if there is ligation and production of recombinant DNA, it is the empty vector which will further transform your host cells.

You do not have the possibility of selecting the cells which received the recombinant DNA by insertional inactivation.

this is a summary of what i got by searching

Phosphatase treatment is commonly used in molecular cloning to prevent self-ligation of vector DNA. However, in your case, it seems that self-ligation is still occurring despite the treatment. Let’s explore the possible reasons for this:

Remember that troubleshooting molecular cloning can be intricate. Double-check your experimental steps, and consider repeating the experiment with slight modifications. If the problem persists, consult colleagues or seek expert advice. Happy cloning! 🧬🔬