Question

What are the principles of regulation of gene expression in prokaryotes? use examples.

Answer 1

Principles of Gene regulation in Prokaryotes

In prokaryotes the regulation of transcription takes place with helps of operon which consists of regulatory DNA sequence that acts as binding site for regulatory proteins. This either inhibits or promotes transcription. There are some operons that are inducible and can be turned on by presence of a particular small molecule. There are operons that are repressible and can be turned off by a small molecule.

The operons contains number of genes and regulatory DNA sequences which control transcription of the operon. The sequences binds to the regulatory proteins that control the operon. The promoter or site where RNA polymerase binds is an example of the regulatory DNA sequence.

The operons might be inducible or repressible:-

Some operons are off but can be turned on by a small molecule. This molecule is known as inducer and the operon is called as inducible. Example – The lac operon is an inducible operon which encodes enzymes for the process of metabolism of lactose. When there is lactose sugar present, it turns on the operon. The other type of operon is the repressible operon like the trp operon which encodes enzymes for synthesis of the amino acid tryptophan. The operon is expressed by default, but can be repressed due to high levels of amino acid tryptophan.