Hi Miray,

when I have a look on your gel images I can hardly see any insert band in the first gel.

However, there might be something on the second gel.

Do you pipett the Ethidium bromide directly in the agarose for your gel before electrophoresis?

I am asking this because ethidium bromide is positivly charged and migrates from the plus to the minus pole. This means that the ethidium bromide concentration at the end of your gel (at the plus pole) will get lower during electrophoresis and small bands can get very faint (like you insert) while bigger bands (like your vector) exhibit still a strong staining.

To overcome this problem you can restain your gel with Ethidium bromide after electrophoresis.

If this is not the problem a mixture of empty vector and vector is a possibilty - in this case you can retransform your DNA and screen for positive colonies.

For me it doesn't look like incomplete digestion - bbecause I don't see additional bands which might indicate this.

I hope this helps