What is the Difference Between Operon and Cistron?

The main difference between an operon and a cistron lies in their structure and function. Here are the key differences:

1. Structure: An operon is a functional unit of DNA that contains a group of genes under the control of a single promoter, while a cistron is a segment of DNA that encodes a single protein. An operon contains multiple structural genes (cistrons).
2. Function: An operon is a regulatory system that allows for the coordinated expression of multiple genes, saving energy by transcribing multiple proteins at once. In contrast, a cistron is an individual gene that translates into a functional polypeptide.
3. Transcription: An operon produces a polycistronic mRNA, which can be translated into separate proteins, while a cistron produces a monocistronic mRNA in eukaryotes, translating into a single protein.

In summary, an operon is a regulatory system consisting of multiple genes tightly regulated by a single promoter, while a cistron refers to a single gene and its associated functions. Operons are found primarily in bacteria and archaea, while cistrons are used as an alternative name for genes in all organisms.

Comparative Table: Operon vs Cistron

Here is a table comparing the differences between an operon and a cistron:

In summary, an operon is a regulatory system that consists of multiple structural genes (cistrons) under the influence of a single promoter and operator, while a cistron refers to a single gene with its associated regulatory elements.