Question

If there is a constitutive mutation is lacO but there is a high level of glucose, will the lac operon be expressed?

Answer 1

Lactose contain two monosaccharide glucose and galactose. Bacteria have a different preference over their need for glucose and lactose. When both glucose and lactose are present , bacteria utilizes glucose instead of metabolizing lactose and inhibit enzymes for lac operon known as glucose effect resulting in diauxic growth. This is repressive effect of glucose on lac operon. So even though constitutive mutation is present in lac operon it will still utilize glucose first than lactose.