Question

According to the operon concept, the regulatory gene regulates the chemical reactions of the cell by

• A. Inactivating enzymes in the reaction
• B. Inhibiting transcription of mRNA
• C. Inhibiting migration of mRNA into cytoplasm
• D. Inhibiting the substrate in the reaction

Answer 1

Answer: (B)

Inhibiting transcription of mRNA

• An operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter.
• The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm or undergo trans-splicing to create monocistronic mRNAs that are translated separately.
• The regulatory sequence produced by the regulatory gene is called a repressor molecule. It binds to the operator or silencer region of the operon and controls the expression of structural genes by inhibiting its transcription.
• Thus, the regulator gene regulates by inhibiting the transcription of mRNA.