Experimental data on transgenic animal production using transfected sperm a
re reviewed. Pathways for further improvement of the method for increasing
the frequency of transgenic organisms are proposed: modification of the sac
charophosphate skeleton and DNA ends; use of nucleic exchange enzymes and d
irected oligonucleotides; use of adhesive sequences (MAR elements), ori rep
lication, and transposable elements within the transgenes; development of t
he embryos selection; the use of gene targeting elements; and the use of va
rious DNA conformations. The promising use of spermatozoa as'a noninvasive
system of gene delivery in transgenesis and prenatal gene therapy are outli
ned.