In the $lac$ operon,the structural genes are switched off when:

Which of the following enzymes increases the permeability of the bacterial cell to lactose?

Transposons can be used during which one of the following?

Wild-type $E. coli$ cells are grown in a normal medium containing glucose. They are then transferred to a medium containing only lactose as the sugar source. Which of the following changes will occur?

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

Few genes are found in all types of cells of differentiated multicellular organisms of higher classes. These are called: