Question

What conditions will cause high expression levels of lacZ, lacY, and lacA in bacteria?(Choose one of the options)

*High allolactose levels

*Low galactose levels

*High glucose levels

*Low lactose levels

Answer 1

Ans.

High allolactose levels

Explanation :

lac operon contains mainly two types of genes that are structural gene and regulatory gene.

Structural genes are lac Z, lac Y and lac A.

Regulatory genes are operator (lac O), promoter (lac P) and regulator (lac I).

Allolactose is an inducer and lac operon is turned on at the presence of high levels of allolactose. Allolactose as an inducer induces the expression of lac genes.

Regulator i.e lac I can synthesize repressor. In high concentration of allolactose, repressor binds with it (allolactose). As a result the repressor can not bind to the operator region. So, RNA polymerase binds to the operator and starts synthesizing mRNA.

Hence, the answer is High allolactose levels.