Without a promoter, the gene is inactive, but replicated. CaMV is used because it is a powerful motor. The CaMV promoter normally drives the creation of copies of the CaMV-virus. The CaMV promoter is preferred above other potential promoters because it is more powerful than others and is not greatly influenced by environmental conditions or tissue types. The perceived hazards of the CaMV promoter in crop plants include the consequences of recombination and pseudo recombination.
Recombination is the exchanges of parts of genes or blocks of genes between chromosomes.
Pseudorecombination is a situation in which gene components of one virus are exchanged with the protein coats of another. Frequently viruses may incorporate cellular genes by recombination or pseudorecombination. It has been noted that such recombinants have selective advantages. The designers of the experiment questioned the safety of transgenic plants containing viral genes . Recombination between CaMV viruses involves the promoter and may take place either between DNA and DNA or RNA and RNA and frequently creates more severe infections than either parent .