Quiz 14: Gene Regulation in Bacteria


Constitutive- the term represents the continuous system of certain productions. The constitutive genes are called as the unregulated genes , which is continuously transcribed the proteins for the normal system functions of the bacterium (or to lead the normal life system); which means those genes requires for the essential need for the existence of a bacterium. This can be explained by all the life forms are made up of the structural and functional proteins, the basic anatomical buildup proteins are the necessary proteins which is called as the structural proteins, the physiological need of certain proteins are all the functional proteins, those necessary proteins are the transcribed by the constitutive genes. In other terms the level of expression of constitutive gene is Constant. Regulated genes are genes which transcribe the proteins only when the bacterium/cell requires. For example if the bacterium is subjected to the certain environment of nutrients rather than the usual system of the bacterium, those cells are gone for the new adaptation forms, generate the regulated genes. In simple terms the regulated genes expressed only the organism requires, whereas the constrictive genes expressed continuously for the existence of lifE.

The figure 14.7 represents the Internal Inducer hypothesis. A. ONPG- O rtho- N itro p henyl - G alactosidase; is the substrate which digested by the -galactosidase enzyme to produce the yellow color which gives the indication of the presence of the -galactosidase. ONPG- Ortho-Nitrophenyl -galactosidase, is the colorless compound which cleaves by the -galactosidase and produce the ortho-nitrophenol and the galactose. The ortho nitrophenol is responsible for the yellow color. If the result of the experiment doesn't gives the yellow color reflects the strain got mutations in genes, which is responsible for the protein -galactosidasE.Now according to the experiment, upon the four tubes of the strains, one of the tube is colorless because of the expression of the lac operon is suppressed by the repressor; so there is no production for the -galactosidase, and there is no action of the ONPG to give the color changE.Other methods to measure the level of expressions are: 1. Usage of Radiolabelled lactose to the cells will gives the data regards the uptake of lactose through the radioactivity measurements of the cells. 2. By applying the Northern blotting technique to study the expression level through the RNA isolated from the bacterium. 3. Also, by applying the Western blot technique to measure the proteins produced by the expression of the Lac operon. B. The results shows the optical density of the merozygote is above 200% because of the rate of expression is high due to the presence of the twice Lac Z genes gives the better yield of -galactosidase, can able to cleave the ONPG- Ortho-Nitrophenyl -galactosidase to give the strong yellow color, which reflects on the optical observation.

The protein synthesis is the series of the process, where the DNA replicates and forms the mRNA which is said to be the transcription, and this transcribed mRNA meets the tRNA codons to synthesize the peptide, the overall phenomenon is said to be the central dogmA.Consider a small sequence of the gene which encodes to the peptide, from gene to mRNA, the regulatory proteins which are the proteins transcribed from the same gene cluster before the initiation of the overall process of the transcription and the translation. The regulatory proteins are two categories, like repressor, and activator. Activator increases the rate of transcription, whereas the repressor suppress the transcription by binding the operator sites in the DNA, While the transcription there is some phenomenon called as the attenuation, attenuation is nothing but the termination of the process by certain extent. In the process of the translation, the mRNA translates to the protein, has some factors like the translational repressor proteins; this proteins can repress the translation by binding to the mRNA. Riboswitches are the genetic switches produce the RNA, which prevents the translation. Antisense RNA is also one of the regulatory mechanisms where the RNA totally reverses and provides the shutdown of the translation. After protein formation, there are some regulatory mechanisms like the feedback inhibition where the shutdown of the protein synthesis takes placE.The significance of the gene regulation in the positive control and the negative control, of course the organism plays the regulation by itself for the survival, here the advantage is the positive control, which means there is no shutdown of any process by the environmental changes the disadvantage is the repression of the synthesis. The repression is not exactly the negative approach it is one of the part which plays in the regulation, because the regulation denotes the control. In spite of this regulation only the organism able to synthesize the necessary proteins for its survival under the controlled manner.

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