Difference between sticky end and flat end:
After cutting with restriction enzyme, the end that is flush is the flat end, and the one that is long and one that is short is the sticky end according to Restriction endonuclease After cutting the end of the product produced by DNA, it was found that there are two ways for restriction endonuclease to cut DNA, namely flat cut and cross cut. The so-called flat cut refers to the cutting of restriction endonuclease at the same position of DNA double strand DNA molecule The resulting end is a flat end. Cross cutting refers to that restriction endonuclease cuts DNA at different positions of DNA double strand, and the ends of the resulting DNA fragments are not even. 
