Question

What is positive regulation?

Answer 1

Hint: Genes of an Organism produce specific proteins or enzymes which in turn, produce specific phenotypes. Structural genes are those genes whose mRNA transcripts are transcribed into a protein. Each cell of an organism possesses all the structural genes, but only a small fraction of them are functional at a given time in a cell. Controlling the activity of genes in a manner such that only those genes are active whose products are required in a cell at a given time is called gene regulation.

Complete answer:
Gene regulation are of two types:
1. Negative regulation and 2. Positive regulation
1. Negative Regulation: An inhibitor known as a repressor is present in the cell or the system, that prevents transcription by inactivating the promoter. For initiating the transcription, an inducer is required. Inducer is an antagonist of the repressor. In negative Regulation, the presence of the product decreases the enzyme synthesis and the absence of the product increases the enzyme synthesis.
In negative gene regulation, the genes continue expressing their effect till their activity is suppressed. This type of gene regulation is also called repressible regulation. The repression is due to a product of regulatory genes.
2. Positive regulation: An effector or activator molecule which may be a protein or a molecular complex activates the promoter for transcription. DNA bound activators can ignite the regulation of transcription by tethering RNA polymerase to the promoter. The operon will be turned off when the positive regulatory protein is absent or inactivated.
The CAP-cAMP system is an example of positive control, because lac operon will be expressed only in the presence of an activating signal- in this case, the interaction of the CAP-cAMP complex with the CAP region acts as an activating signal.
Positive gene regulation is the one in which genes remain non-expressed unless and until they are induced to express.
In a biosynthetic pathway negative mechanism operates (e.g., Lac operon) while in a degradative system, either negative or positive mechanism may operate.

Note:
In gene expression, a gene is able to express itself in the phenotype of an Organism. Gene expression is the mechanism at molecular level which involves biochemical genetics. It consists of synthesis of RNAs, polypeptides, structural proteins , biochemicals or enzymes which control the functioning of specific traits. In gene regulation, genes are switched on and off depending upon the requirement of the cell and the state of development.