Question

Which of the following controls the rate of m – RNA synthesis ?

• A. Operator gene
• B. Structural gene
• C. Promoter gene
• D. Regulator gene

Answer 1

The correct option is C Promoter gene

The promoter gene is the DNA segment at which RNA-polymerase binds. It initiates the transcription of the structural genes. It controls the rate of mRNA synthesis.

Promoter sequences define the direction of transcription and indicate which DNA strand will be transcribed; this strand is known as the sense strand. Promoters are a vital component of expression vectors because they control the binding of RNA polymerase to DNA. RNA polymerase transcribes DNA to mRNA which is ultimately translated into a functional protein.

Promoter gene acts as an initiation signal which functions as recognition center for RNA polymerase provided the operator gene is switched on. RNA polymerase is bound to the promoter gene. When the operator gene is functional, the polymerase moves over it and reaches the structural genes to perform transcription. When repressor is not able to block operator gene then active protein will be produced by regulator gene.

So, the correct option is 'promoter'.