BIOLOGICAL ORDER 



1 - Inductivity i+ dominant 



operator + sensitive to repressor 

 no/3 -golactosidase 

 no permease 



2ond3-Constitutivity I- dominant 

 operator 0^ insensitive to repressor 



2- 0'^/Z-*-y* in c/s 

 fi -galactosidase present 

 permease present 



0VY+ inr/5 

 permease present 

 0<^/Z + in trans 

 no /3 -galactosidase 



^ •yj-galactosidase Opermease x repressor 



Figure 21. The Operator Gene. 



1. Inductivity is dominant. The operator is of the wild type (o+) that is 

 sensitive to the repressor. No enzymes are produced by the heterozygote in the 

 absence of an inducer. 



2. Constitutivity is dominant. The genes z+ and y+, located on the same 

 chromosome as the constitutive operator o", are active: both permease and 

 iS-galactosidase are produced in the absence of an inducer, despite the presence 

 of a repressor. 



3. Constitutivity is dominant but only for the gene y+ located on the same 

 chromosome as o'' (position cis) . The gene z+ is located on a chromosome 

 carrying the wild-type operator o+ and is not active. 



i5e^ 



