The ability of genetic elements like gene cassettes to excise and insert into genomes results in highly similar gene regions appearing in distantly related organisms. The three classes of integrons are similar in structure and are identified by where the insertions occur and what systems they coincide with.
Similar genes appearing in distantly related organisms due to the ability of genetic elements like gene cassettes to excise and insert into genomes are a key concept. The three classes of integrons, characterized by their structure and the locations of insertions, are used to identify them.