5: What’s wrong with these gels?

perplexed student

Some mixed up students have recorded their gels incorrectly in their lab books. They should be suspicious of each of the drawings below. Can you tell them why? (This is really a logical exercise, not a maths exercise, which is why I didn’t put any numbers in. You can assume there are no odd conditions like overlapping bands in the same lane, or accidental breakage of the DNA into extra fragments.)