The accessibility of promoter regions of bacterial $DNA$ in many cases is regulated by the interaction of proteins with sequences termed:

Which organism was used by Beadle and Tatum to propose the one gene-one enzyme hypothesis?

Which statement is correct for homeotic genes?

Select two statements out of the four given statements $(i-iv)$ with respect to the $lac$ operon.
$(i)$ Glucose or galactose binds with the repressor and inactivates it.
$(ii)$ In the absence of lactose,the repressor binds with the operator.
$(iii)$ The $Z$-gene codes for permease.
$(iv)$ It was elucidated by Francois Jacob and Jacques Monod.

Which of the following is true for a repressible operon?

In $Escherichia \ coli$,$lac$ operon is induced by