Chapter 28, Problem 8E

(a)

Summary Introduction

To explain: The reason why an inactivation of O₂ or O₃ sequence of the lac operon causes only a two-fold loss in repression.

Introduction: Operon contains coding DNA sequences, regulatory DNA sequences, and the regulatory proteins. Regulatory proteins are both activators (TURN ON) and repressors (TURN OFF). Based on these, operons may be classified as inducible (usually ‘off’) and repressible (usually ‘off’). The lac operon is an inducible operon and controls the metabolism of the lactose sugar through β-galactosidase enzyme.

(b)

Summary Introduction

To explain: The reason why inactivation of both O₂ and O₃ of the lac operon reduces the repression approximately to 70-fold.

Introduction: Operon contains coding DNA sequences, regulatory DNA sequences, and the regulatory proteins. Regulatory proteins are both activators (TURN ON) and repressors (TURN OFF). Based on these, operons may be classified as inducible (usually ‘off’) and repressible (usually ‘off’). The lac operon is an inducible operon and controls the metabolism of the lactose sugar through β-galactosidase enzyme.