The construction in the proof of Thm. 3 has direct implications for the exploration of chemical space. First, it shows that functional groups can be introduced easily into a scaffold of interest. This can usually be achieved by a single cut of size 1 or 2 provided the functional group of interest is already appearing pre-formed in the population or provided as part of the reservoir set. This simple observation suggest to construct GAs for chemical space exploration in such a way that a reservoir set is always kept in the population as means of replenishing diversity that otherwise may be lost throughout a GA run: if an atom-type has been selected out of the population, crossover operators by definition are incapable of recovering it. It can be taken easily from the reservoir set however. In the field of retro-synthetic analysis, Stuart Warren defined a functional group interconversion (FGI) as "the process of converting one functional group into another by substitution, addition, elimination, oxidation, or reduction." In our setting, all these operations can be achieved with degree-preserving cut-and-join crossover. For crossovers restricted to natural joins, however, the mutation operator is required to change bond order, or paths of length 2 need to be replaced by cuts with larger cut-sets.