Based on the functions, genes can be of two types – Inducible genes and constitutive genes.
Inducible gene expression increases as a result of response to inducers. These inducers are tiny molecules. Β-galactosidase, proteins produced by E.coli are referred to as inducible as they are produced in good quantities when “lactose” – a particular inducer is found.
Constitutive genes are constantly expressed in most cells and are not subject to regulation. The produce of such genes are needed in cells all the time. One good example are the enzymes of the citric acid cycle.
Protein making involves two key steps – transcription and translation. Transcription is the phenomena wherein messenger RNA or mRNA is synthesized from the DNA template through RNA polymerase. A gene that is repeatedly transcribed is a constitutive gene. Facultative gene on the other side is the one which is transcribed when required.
Gene transcription is a process that is highly regulated. Constitutive genes are active, always. Ribosomal genes are a good example of this. These are transcribed constantly as ribosomes continually require protein synthesis.
Transcription factors in molecular Biology are proteins regulating the rate of transcription of genetic information from DNA to mRNA. This is brought about by binding to a particular DNA sequence. These transcriptional factors are important as they regulate the genes – switch them on and off so as to ensure genes are expressed at the right time in the right cell with the adequate quantity all through the lifetime of the entity/cell.
Comparing Constitutive Genes and Regulated Genes
Regulated genes are expressed only in some circumstances when required so as to save cellular energy. Constitutive genes on the contrary are expressed always.
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