We propose here a systematic formal study of the splicing operation in
troduced by Head as a model of recombinant behavior of DNA. We conside
r both simple and iterated splicing, with respect to a finite or an in
finite set of splicing rules, in the latter case the whole set of rule
s constituting a regular language. Relations between these operations
and usual operations with languages are investigated, as well as the c
losure of Chomsky language families under these splicing operations. A
series of open problems are formulated too.