Prokaryotes And Eukaryotes: A Genetic Analysis

Gene expression is the process in which the cell interprets its genetic information in the form of DNA to help the protein synthesis. DNA (deoxyribonucleic acid) is a unique genetic blueprint that every living thing has. Prokaryotes and eukaryotes have different way to express their genes. The cell controls how to express their gene to ensure that every proteins and RNA molecule encrypted in its DNA are well managed. Gene expression is needed for both prokaryote and eukaryote to control the mechanism because without gene expression they would produce large quantities of proteins ceaselessly.1

Gene Expression in Escherichia coli

One of the examples for prokaryote is Escherichia coli. Inducible system is required, as a system to control when

coli is one of the best examples of the inducible system known as lac operon. Operon word itself refers to the control mechanism, and lac stands for lactose or milk sugar which the presence will activate the system. Lac operon can be classified as both positive and negative control mechanism. Positive transcriptional control means that DNA-binding form turns on the gene, on the contrary negative control mechanism means that DNA-binding form turns off the gene.2

For the positive control, CAP (catabolite activator protein) is required before RNA polymerase binds also known as transcriptional activators, while in negative control known as transcriptional repressor.2E. coli use lactose, -galactoside encode by lacZ is induced due to the presence of lactose, as their energy and carbon source after being broken down into glucose and galactose. They use -galactosidase as an enzyme, include lac permease, to catabolize and is involved in the lactose transportation inside the cell, and transacetylase to metabolizes another disaccharides.3-galactosidase permease encoded by lacY and -galactoside acetyltransferase encoded by lacA.-galactoside acetyltransferase acts as a cell protection from the buildup of toxic products as the results of -galactosidase activity.2,3,5Those three lac genes are neighboring to each other. There are also two comparatively short segments of DNA in lac operon’s control region. First, the promoter is the region in which RNA polymerase takes

I gene, as a regulatory gene, encodes a repressor protein that acts as an on-off switches. The process in lac operon is first the I gene produces a repressor that will bind to the operator. The active repressor itself binds to the operator results in blocking the RNA polymerase from transcribing. With the presence of lactose, the active repressor will change its shape into the unfit shape for operator so it will unbind to the operator site due to lactose binds to another part of active repressor. RNA polymerase will then be able to initiate transcription and the structural genes will be transcribed to form mRNA that later translate into enzyme that will break down lactose.Lac operon will be activated when the amount of glucose decreases and CAP will turn on lac operon. In contrast, when the glucose level is low, cAMP (cyclic adenosine monophosphate) produced from ATP. CAP binds to the cAMP forming CAP-cAMP, and it later binds to the promoter and induced the