Question

Compare and contrast regulation of gene expression with use of an enzyme inhibitor. List one advantage and disadvantage for regulating gene expression and one advantage and one disadvantage for using inhibitor.

Answer 1

Positive gene regulation controls the production of genes by switching them on.

In negative gene regulation controls the production of genes by switching them off.

Positive gene regulation allows for the production of a gene which is required for use at a certain period of time in a cell.

Negative gene regulation prevents the overproduction of a gene at a certain period of time in a cell.

Example: In E. coli both the Ara operon and the lac operon are induced by sugar, but lac operon is controlled by a repressor and hence negative regulation whereas in Ara operon is positively regulated by a transcriptional activator.

For controlling gene expression an inducible system is normally easier to regulate because it needs to incorporate an inducer to turn on gene expression, whereas in a co-repressible system it would need to remove the co-repressor.

The key difference between a negatively regulated and a positively regulated system is in terms of the behavior of the regulatory protein. The issue with a negatively regulated system is that for controlling a multi copy plasmid excess amount of repressor is required, and a single copy of the repressor gene on the chromosome is not sufficient.

In negatively regulated promoters are not as tightly regulated and will have considerable amount of basal expression.

In positive regulation they are more tightly regulated and the basal uninduced expression levels are usually lower.