Each ce
ll of a living organism contains thousands of genes. But all genes do not function at a time. Genes function according to requirements of the cell. Genes control the phenotypic expression of various characters through the production of specific enzymes. Enzymes are special proteins which catalyse chemical reactions. The production or synthesis of a particular enzyme is not constant. It varies as per the requirement of the cell in other words, the synthesis of a particular enzyme is sometimes high and sometimes low depending upon the requirement of the cell. Thus, there exists an on-off system which regulates protein synthesis in all living cells. The precise study of this on-off mechanism is called regulation of gene action or regulation of gene expression or regulation of protein synthesis. Synthesis of enzyme depends mainly on two factors. In a degradative process, the synthesis of enzyme depends on the availability of the molecule to be degraded. If the molecule is in more quantity, the enzyme synthesis will be more and vice versa. In a biosynthetic pathway, the synthesis of an enzyme is governed by the end product. If the end product is more, the enzyme synthesis will be less and vice versa.
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