 If such a phenotype is found then it can be assumed that the insertion has caused the gene relating to the usual phenotype to be inactivated.Because the sequence of the transposon is known, the gene can be identified, either by sequencing the whole genome and searching for the sequence, or using the polymerase chain reaction to amplify specifically that gene.Because many viruses integrate their own genomes into the genomes of their host cells in order to replicate, mutagenesis caused by viral infections is a fairly common occurrence.