Constitutive Transcription

Based on the functions, genes can be categorized into two types – Inducible genes and Constitutive genes.

Inducible gene expression increases in response to inducers, which are small molecules. An example of an inducible gene is Β-galactosidase, a protein produced by E. coli in large quantities when a specific inducer, such as lactose, is present.

Constitutive genes are constantly expressed in most cells and are not subject to regulation. The products of such genes are needed in cells all the time. One good example is the enzymes of the citric acid cycle.

Overview

Protein synthesis involves two main processes - transcription and translation. Transcription is the process where mRNA is created from a DNA template with the help of RNA polymerase. A gene that is transcribed all the time is referred to as a constitutive gene, while a facultative gene is one that is transcribed only when needed.

Gene transcription is a highly regulated process. Constitutive genes are always active, and ribosomal genes are a prime example of this; they are constantly transcribed in order to maintain a continuous supply of proteins for synthesis.

Transcription factors in molecular Biology are proteins that control the rate of transcription of genetic information from DNA to mRNA. These proteins bind to a particular DNA sequence, allowing them to regulate the genes by switching them on and off to ensure that genes are expressed correctly at the right time, in the right cell, and with the correct quantity throughout the lifetime of the entity/cell.

Comparing Constitutive and Regulated Genes

Regulated genes are expressed only under certain conditions, in order to conserve cellular energy. On the other hand, constitutive genes are expressed at all times.

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