lacl prevents the repressor polypeptide is a mutant that prevent operon from binding lactose, and thus will bind to the operator and be non-inducible.. This mutant will represses the lac operon whether lactose is present or not and the lac operon will not be expressed. It is also called“super-supperesor".
The lacI locus – One type of mutant allele of lacI (callled I-) prevents the production of a repressor polypeptide or produces a polypeptide that will not allow to bind to the operator sequence.
This is also a constitutive expresser of the lac operon because absence of repressor binding permits transcription.
The best way to determine if these populations form part of the same species is to study the existence of reproductive isolation between populations. Moreover, the result of an experiment based on the study of reproductive barriers may be complemented with molecular biology approaches that determine the level of sequence homology between populations
