Question

Which of the following statement is incorrect with respect to operons?

• A. Operon is a coordinated group of genes that function together
• B. All genes of an operon are present downstream of a single promoter
• C. Operons are characteristic of eukaryotes and are absent in prokaryotes.
• D. Operons may either be inducible or repressible in nature.

Answer 1

The correct option is C Operons are characteristic of eukaryotes and are absent in prokaryotes.

Although prokaryotes are relatively simple organisms, their genomes are highly organised.

Prokaryotic genes are polycistronic, as multiple genes may need to be transcribed simultaneously. Operons help organise the genes this way.

Eukaryotic genes are monocistronic, and thus, typically have an individual promoter and terminator for every gene. Hence, operons are mostly a characteristic feature of prokaryotes and rarely, found in eukaryotes.

Each operon has a single promoter, downstream of which are found the operator and structural genes. Operons may either be inducible (like the lac operon of E.coli) or repressible (e.g., tryptophan or trp operon of E.coli) in nature.