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It is the allele number that defines a particular mutation. Insertion mutations on extrachromosomal elements are designated with zz, followed by a letter denoting the element used. For example, zzf is used for insertion mutations on an F’ plasmid. Insertions with an unknown location are designated zxx. Allele designation of insertion mutants in unknown genes based on chromosome map location: zaa ¼ insertion at 0–1 min zab ¼ insertion at 1–2 min zac ¼ insertion at 2–3 min zad ¼ insertion at 3–4 min zae ¼ insertion at 4–5 min zaf ¼ insertion at 5–6 min zag ¼ insertion at 6–7 min zah ¼ insertion at 7–8 min zai ¼ insertion at 8–9 min zaj ¼ insertion at 9–10 min zaa–zaj ¼ insertion in 0–10 min region zba–zbj ¼ insertion in 10–20 min region zca–zcj ¼ insertion in 20–30 min region zda–zdj ¼ insertion in 30–40 min region zea–zej ¼ insertion in 40–50 min region zfa–zfj ¼ insertion in 50–60 min region 6 strain collections and genetic nomenclature [1] zga–zgj ¼ insertion in 60–70 min region zha–zhj ¼ insertion in 70–80 min region zia–zij ¼ insertion in 80–90 min region zja–zjj ¼ insertion in 90–100 min region zxx ¼ insertion with unknown location zzf ¼ insertion on F–plasmid A few commonly used minitransposon derivatives are designated as follows: Tn10dTet ¼ Tet resistance, deleted for Tn10 transposase Tn10dCam ¼ Derived from Tn10dTet, Cam resistance substituted for Tet resistance Tn10dKan ¼ Derived from Tn10dTet, Kan resistance substituted for Tet resistance Tn10dGen ¼ Derived from Tn10dTet, Gen resistance substituted for Tet resistance MudJ ¼ Kan resistance, forms lac operon fusions, deleted for Mu transposase MudJ‐Cam ¼ Derived from MudJ, Cam resistance marker disrupts Kan resistance MudCam ¼ Cam resistance substitution between ends of Mu Plasmids When writing the genotype of a strain, plasmids are often indicated by a slash (/) after the chromosome genotype.

To isolate insertions in or near a gene, cells with transposon insertions are first selected by plating onto a rich medium containing an antibiotic resistance expressed by the transposon. The resulting colonies can then be screened for insertion mutations in a gene or insertions near a gene. An example of how to isolate insertions near a gene is shown in Fig. 2. cis Complementation Many transposases act preferentially on the DNA from which they are expressed. Often they must be expressed at high levels to work effectively in transposition.

The transposon is carried on a suicide plasmid). The plasmid can be transferred from the permissive host to the nonpermissive host by conjugation, transformation, or electroporation, with selection for an antibiotic resistance encoded by the transposon. 14 transposons [2] Overexpression of Transposase in trans The frequency of transposition can often be improved by increasing the concentration of transposase in the cell. For example, the transposase gene(s) can be cloned from a transposon into a vector that places their expression under the control of an easily regulated promoter, such as the tac promoter or the ara promoter.