Validate the ΦBT1 integrase can invert genetic elements flanked by
attB and attP recognition sites. Three transcriptional units,
consisting of a positive control, negative control, and test unit, alongside
wild-type yeast are used. LacZ replaces the SSP to conduct a
colorimetric assay using ONPG. β-Galactosidase cleaves ONPG to form a yellow
substrate. Reverse LacZ with attB and attP sites is placed
downstream of integrase. If integrase successfully inverts this construct,
forward LacZ is formed, placing the ATG start codon in frame of a strong
promoter, causing the production of β-Galactosidase, indicated by a yellow
color change.