The present invention provides a molecular mechanism for gene containment in sexually reproducing transgenic plants. The mechanism is achieved with a molecular construct comprising a blocking construct (BC) that is inserted fully or partially into an intron of a transgene of interest (TGI). The TGI encodes desired gene products, such as heterologous or homologous proteins, peptides or other useful products. The expression of the BC leads to block of at least one molecular or physiological function that is essential for development or reproduction of the transgenic plant. Thereby the BC expression leads to death or incapacity of sexual reproduction of the plant. Moreover, the mechanism comprises an externally applicable recovering tool to recover the functions blocked by the BC. The recovering tool may be a recovering construct (RC).