Question

Discuss in detail the two different types of operons found in bacterial genomes (inducible operons and repressible operons) and describe how they work. Then describe the three different forms of prokaryotic genetic recombination discussed in the commentary Prokaryotic Genetic Recombination. Hypothesize how recombination might adversely affect the functioning of an operon such as the lac operon or the trp operon. What might be the metabolic implications for an E. coli cell that experiences a disruption of one of these operons?

Answer 1

Ans:

Two different types of operons found in bacterial genomes (inducible operons and repressible operons):

Inducible operons:

- Inducible operon is one that is expressed in the presence of a substance termed inducer.

- An inducer is a small molecule that triggers gene transcription by binding to a regulatory protein.

- For example: the lac operon is an inducible operon.

- In lac operon, lactose and its analogs that lead to the expression of the lac genes are termed inducers and the relief of repression for operon is termed induction.

Repressible operons:

- Operons can be turned "off" by a small molecule. The molecule is called a corepressor and the operon is said to be repressible.

- For example: the trp operon is a repressible operon.

- This operon is expressed by default, but can be repressed when high levels of amino acid tryptophan are present.

- The corepressor in this case is tryptophan.

- Thus, some operons are inducible, meaning that they can be turned on by the presence of a particular small molecule. Others are repressible meaning that they are on by default but can be turned off by a small molecule.