Why the operon is common in prokaryotes not in eukaryotes?

Answer 1

Prokaryotes are small organisms which live in a rapidly changing environment. The most important thing for them is to react in a quick and accurate way to the ever changing conditions. For example a bacterium lived in a place where Glucose was abundant, suddenly it disappeared and only lactose has left. Now it has to switch very fast to lactose usage. The best thing is to turn on all the genes related to lactose at the same time, in order to stay alive. When Glucose comes back all those genes have to be turned off at the same time to avoid waist of energy.

Eukaryotes occupy a different Ecological niche; they are more complex and more dependant of each other then Prokaryotes. They do not have to react so fast to environment- they have each other, but they have to make sure that everything is done correctly to prevent large damage to the organism. It means they need very tight supervision on everything or in other words Regulation. Individual promoters give the ability to make a much finer regulation.

Also,Unlike prokaryotes, the mRNAs of eukaryotes contain introns which have to be removed and the mRNA modified before it is been translated.

Answer 2

Operons are common in prokaryotes because their DNA is organized into operons, where multiple genes are transcribed together under the control of a single promoter. Eukaryotes have more complex gene regulation mechanisms, with genes organized individually and controlled by their own regulatory elements, leading to less reliance on operons for coordinated gene expression.