Final answer:
On an agarose gel without restriction enzyme digestion, you would see a single band representing undigested DNA, as opposed to multiple bands showing the pattern of fragments that would result from successful digestion.
Step-by-step explanation:
If restriction enzymes were not added or the digestion was unsuccessful, on an agarose gel you would typically see a single band representing undigested DNA. Without the action of restriction enzymes, the DNA molecule would not be cleaved into smaller fragments, which would otherwise migrate at different rates during gel electrophoresis and produce a pattern of multiple bands. Since restriction digestion did not occur, the undigested DNA, being larger in size, would move slowly and form a band near the well, rather than displaying a characteristic banding pattern expected from restriction enzyme digestion.
In the context of restriction mapping or RFLP analysis, a single band indicates that the sequence of DNA bases has not been cleaved, which means that the probed region has not been successfully digested. Therefore, you would not be able to observe the differences in distribution of restriction enzyme recognition sites or compare the DNA samples based on distinct banding patterns.