Trans-acting or cis-acting mutation help.

PaJaMo experiment.

Constructing Partially Diploid cells in which the section of the chromosome from a wild type cell carrying the Jun genes was intorduced into cell carrying mutant version of Jun genes.

Now when the chromosomal genes are constitutively expressed,
In case of trans-acting factor : Because of a mutation in JunA gene, the wild type copy restores the actual function.
In case of cis-acting element : mutation causing constitutive expression in Jun operator, it could not be complemented by trans factor. The operator functions only in cis.