04 Molecular Basis of Inheritance - part 10 - Regulation of gene expression

04 Molecular Basis of Inheritance - part 10 - Regulation of gene expression


Regulation of gene expression: 

  • It is the multistep process by which a gene is regulated and its product is synthesized. Thus, gene expression results in the formation of a Polypeptide. 
  • Gene expression process is regulated at different levels. 
  • In eukaryotes, the regulation can be at different levels like-
  1. Transcriptional level (formation of primary transcript) 
  2. Processing level ( regulation of splicing) 
  3. Transport of m-RNA from nucleus to the cytoplasm. 
  4. Translational level.
  • Genes of a cell are expressed to perform different functions. For eg. An enzyme beta galactosidase is synthesised by E-coli. 
  • It is used for hydrolysis of lactose into galactose and glucose.
  • If E.coli bacteria do not have lactose in the surrounding medium as a source of energy, then enzyme b-galactosidase is not synthesised. 
  • So, it is the metabolic or physiological or environmental conditions that regulate expression of genes. 
  • The development and differentiation of embryo into an adult organism, is also a result of the coordinated regulation or expression, of several sets of genes. 
  • Now one has to understand and know the mechanism by which the organisms regulate gene expression in response to changes in the environment. 
  • If so, whether single mechanism exists for regulation of the expression of different genes/ sets of genes or different genes are regulated by different mechanisms. 
  • Certain bacteria like E.coli adapt to their chemical environment by synthesizing certain enzymes depending upon the substrate present. Such adaptive enzyme is called inducible enzymes. 
  • A set of genes will be switched on when there is necessity to metabolise a new substrate. This phenomenon is called induction and small molecule responsible for this, is known as inducer.
  •  It is positive control.
Do you know ? 
  • Repressible regulation of gene is seen when the end product of a biosynthetic pathway like amino acid, is provided in the medium. 
  • At this time, internal biosynthesis of amino acid stops. 
  • It is negative control so the metabolite (amino acid) turns off a set of genes involved in producing that metabolite. This is called feedback repression.



Comments

Post a Comment

Popular posts from this blog

6. Biomolecules - part 01 - Carbohydrates

Image
  6. Biomolecules - part 01 - Carbohydrates Introduction : Our planet is having a wide diversity of living organisms that are classified as - unicellular  (consisting of a single cell; including bacteria and yeast) or  multicellular  having many cells (e.g. plants and animals).  living organisms have cell as the basic structural and functional unit.  The cells have protoplasm containing numerous chemical molecules, the biomolecules. Biochemistry  : Biochemistry is  biological chemistry  that provides us the idea of the chemistry of living organisms and molecular basis for changes taking place in plants, animals and microbial cells.  It develops the foundation or understanding  all biological processes  and communication within and between cells as well as chemical basis of inheritance and diseases in animals and plants. Chemical analysis of all living organisms indicates presence of the most common elements like  carbon, h...
Read more

6. Biomolecules - part 02 - Lipids

Image
  6. Biomolecules - part 02 - Lipids B. Lipids : These are group of substances with greasy consistency with  long hydrocarbon chain containing carbon, hydrogen and oxygen. In lipids, hydrogen to oxygen ratio is  greater than 2:1  (in carbohydrates it is always 2:1). Lipid is a broader term used for fatty acids and their derivatives.  They are soluble in organic solvents (non-polar solvents).  Fatty acids are organic acids which are composed of hydrocarbon chain  ending in carboxyl group (-COOH).  They can be  saturated fatty acids  with no double bonds between the carbon atoms of the hydrocarbon chain.  Palmitic and stearic acids  found in all animal and plant fats are examples of saturated fatty acids. Unsaturated Fatty Acids  are with one or more double bonds between the carbon atoms of the hydrocarbon chain.  Oleic acid  found in nearly all fats and  linoleic acid  found in many seed oils are example...
Read more

6. Biomolecules - part 05 - Enzymes

Image
  6. Biomolecules - part 05 - Enzymes Enzymes : Thousands of different chemical reactions take place automatically at a given time in a tiny living cell. The reactions take place at the body temperature.  If these enzymes were not present in the cell, either the reactions would not occur or if they occur they would occur at a  very very slow rate . Know the scientists : German chemist  Edward Buchner  discovered enzymes by accident.  Buchner discovered that living cells were not necessary but that  yeast  extract could bring about fermentation.  He then coined the term Enzyme (Gk. En = in, zyma = yeast i.e. in yeast). This term is now commonly used for all biocatalysts. Each enzyme catalyzes a small number of reactions, specifically perhaps only one. Substrate :  The substance upon which an enzyme acts is termed as the substrate.  Endo-enzymes :  The enzymes which act within the cell in which they are synthesizedare known as en...
Read more