The method is based on the fact that RNA with specific undermodifications accumulates under nonpermissive growth conditions and that such a defect can be detected by remodification either in vivo at permissive conditions or in vitro.
Source: wiktionary
The possibility that undermodification of A-37 in tRNA may further affect metabolism through frameshifting events might also be considered.
Source: wiktionary
If the grain is embedded with the ventral side up in the plastic, a shallow grinding will suggest undermodification, whereas a heavier shaving will register overmodification.
Source: wiktionary