What does '$3$' represent in the given figure?

Transposons can be used during which one of the following?

In the lac operon, the $z$ gene codes for:

Which of the following does not act as an inducer in the $lac$ operon?

Select the two correct statements out of the four $(i-iv)$ statements given below about the lac operon.
$(i)$ Glucose or galactose may bind with the repressor and inactivate it.
$(ii)$ In the absence of lactose,the repressor binds with the operator region.
$(iii)$ The $z$-gene codes for permease.
$(iv)$ This was elucidated by Francois Jacob and Jacques Monod.
The correct statements are:

What is the location of the product of the $Lac \, y$ gene?