You have isolated two different mutants reg1 and reg2 each c

You have isolated two different mutants (reg1 and reg2), each causing constitutive expression of the emu operon (emu1 emu2). One mutant contains a defect in a DNA-binding site, and the other has a defect in the gene encoding a protein that binds to the site (loss of function]. Is the DNA-binding protein a positive or negative regulator of gene expression? (practice with related question 17 on textbook page 335, 2^nd ed.).

Solution

In case of negative regulation the expression gene gets blocked when repressor protein binds at operator site. In other way Positive regulation represent gene get expressed after binding of transcription factor.

As per given expression detail. The productive results of change in DNA binding site are not mentioned. In other result they mentioned that protein formed but loss of function. Loss of function is due to change in translation initiation site. Change DNA-binding site work as negative regulator because change in DNA binding site will result in loss of expression of gene. It may alter the function of expressed gene.