In the Southern blotting method, after cutting with restriction enzymes, running in a gel, and staining the gel to visualize the digest (this is before transferring to membrane), it is important to look for the following when evaluating a digest:
1) The presence of distinct bands corresponding to the target DNA fragments
2) The absence of smearing or spurious bands
3) The presence of a ladder pattern indicating the size of the fragments
4) All of the above