BME494s2013 Project Team1: Difference between revisions
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<!-- Background information on the natural Lac operon. This should be based on Group Presentation 2 --> | <!-- Background information on the natural Lac operon. This should be based on Group Presentation 2 --> | ||
The lac operon itself is a set of genes found in certain bacterias' DNA that is required for the transport and metabolism of lactose. Most commonly found in Escherichia coli, the operon was the first example of a group of genes under the control of an operator region to which a lactose repressor binds. | The lac operon itself is a set of genes found in certain bacterias' DNA that is required for the transport and metabolism of lactose. Most commonly found in Escherichia coli, the operon was the first example of a group of genes under the control of an operator region to which a lactose repressor (LacI) binds. | ||
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The Lac operon functions as a single transcription unit and is comprised of an operator, a promoter, and one or more structural genes such as a regulator or terminator that are transcribed into one polycistronic mRNA. When the bacteria are transferred to lactose-containing medium, allolactose (which forms when lactose is present in the cell) binds to the repressor, inhibits the binding of the repressor to the operator, and allows transcription of mRNA for enzymes involved in lactose metabolism and transport across the membrane. | The Lac operon functions as a single transcription unit and is comprised of an operator, a promoter, and one or more structural genes such as a regulator or terminator that are transcribed into one polycistronic mRNA. Typically, the structural genes include LacZ, LacY, and LacA [2]. | ||
"* '''LacZ''' encodes β-galactosidase, an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose. | |||
* '''LacY''' encodes β-galactoside permease, a membrane-bound transport protein that pumps lactose into the cell. | |||
* '''LacA''' encodes β-galactoside transacetylase, an enzyme that transfers an acetyl group from acetyl-CoA to β-galactosides. | |||
Only '''LacZ''' and '''LacY''' appear to be necessary for lactose catabolism". | |||
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When the bacteria are transferred to lactose-containing medium, allolactose (which forms when lactose is present in the cell) binds to the LacI repressor, inhibits the binding of the repressor to the operator, and allows transcription of mRNA for enzymes involved in lactose metabolism and transport across the membrane as seen in the image. | |||
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The main idea is that E. coli (the most common medium when investigating the Lac operon) conserves its resources by not making Lac proteins when other more easily-accepted sugars, such as glucose, are available [ | The main idea is that E. coli (the most common medium when investigating the Lac operon) conserves its resources by not making many Lac proteins when other more easily-accepted sugars, such as glucose, are available [3]. This was tested by Jacques Monod during World War II. He tested the combinations of different sugars for E. coli and discovered that when the bacteria are grown with glucose and lactose, glucose would get metabolized first during the bacteria's growth phase I and then lactose during growth phase II. | ||
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This means that if glucose and lactose are available for the cell, transcription will occur but at a slow rate. Obviously, if there is no lactose at all, nothing will be transcribed. As long as lactose is available, transcription will happen as the LacI repressor is never binded to the operator. Thus, when these Lac proteins are made with the presence of lactose, the lac gene and its derivatives can be used to trigger a color change within the cell. Onnce glucose is used up, lactose acts as the power source, and the lac operon can truly act as a reporter gene. As in the case for our group, the lac operon device contained the necessary promoters, ribosome-binding sites, terminators, a LacI repressor, a cyano fluorescent protein, and a vector backbone based on the Type IIS assebmly strategy. | |||
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Revision as of 11:48, 28 April 2013
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Overview & PurposeSarah
Background
"* LacZ encodes β-galactosidase, an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose.
Only LacZ and LacY appear to be necessary for lactose catabolism".
Design: Our genetic circuitJulia OUR GENE SWITCH: THE PARTS <tab>pSB1A3-1 is a high copy number plasmid. The replication origin is a pUC19-derived pMB1 (copy number of 100-300 per cell). The terminators bracketing pSB1A3 MCS are designed to prevent transcription from inside the MCS from reading out into the vector.
Building: Assembly SchemeEmily
Testing: Modeling and GFP Imaging
Stakeholder Assessment
SUPPORTS & UNDERSTANDS
Our Team
Works Cited[1] Potts, Michelle. "Microbiology Exam 2." Microbiology Exam 2. N.p., 12 Feb. 2012. Web. 24 Apr. 2013. [2] "Lac Operon." Wikipedia. Wikimedia Foundation, 22 Apr. 2013. Web. 28 Apr. 2013. [3] Muller-Hill, Benno (1996). The lac Operon, a Short History of a Genetic Paradigm. Berlin: Walter de Gruyter. pp. 7–10. ISBN 3-11-014830-7.
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