|+ Glucose/Lactose Relationship to Lac Operon Transcription (2)
|+ Glucose/Lactose Relationship to Lac Operon Transcription (2)
! Carbohydrates
! Carbohydrates
! Activator Protein
! CAP-cAMP Complex
! Repressor Protein
! LacI Repressor
! RNA Polymerase
! RNA Polymerase
! Transcription of Lac Operon
! Transcription of Lac Operon
|-
|-
| + Glucose, + Lactose || Not bound to DNA || <b>Lifted off operator site</b> || Keeps falling off promoter site || Very low transcription
|-
| Cell 2 || Cell 3
| Cell 2 || Cell 3
|-
| Cell B
| Cell C
|}
|}
<br>
<br>
From this table, we can see that transcription of the Lac Operon occurs only when the cell is in the presence of lactose, but <i>not</i> glucose. To digest lactose, the cell needs β-galactosidase, which can only be produced by initiating transcription of the Lac Operon.
From this table, we can observe a multitude of things:<br>
*
see that transcription of the Lac Operon occurs only when the cell is in the presence of lactose, but <i>not</i> glucose. To digest lactose, the cell needs β-galactosidase, which can only be produced by initiating transcription of the Lac Operon.
The Lac Operon is a gene specific to E. Coli that controls the cell's digestion of lactose. It consists of a promoter, an operator, three structural genes, and a terminator. It is both positively and negatively regulated, allowing expression to be contingent on the concentrations of glucose and lactose in the cell.
STRUCTURE
The Lac Operon encodes three structural genes:
LacZ: The Lac Z structural region, or β-galactosidase, hydrolyzes the disaccharide lactose into glucose and galactose, sugars that are smaller and easier for the cell to digest. However, in low concentrations of lactose, β-galactosidase cleaves and rearranges lactose into allolactose, which acts as an inducer for the LacI repressor (see Positive Regulation).
LacY: LacY, or lactose permease, is a transmembrane protein that transports lactose into the cell.
LacA: LacA is a transacetylase. While it has functionality, it has little effect on the function of our design, so it will not be discussed.
In addition to the structural genes, the Lac Operon includes a promoter and an operator region. The promoter region is the area to which the Lac I repressor and the CAP-cAMP complex bind, the mechanics of which will be discussed later (see Positive Regulation and Negative Regulation).
PURPOSE: Efficiency
Expression of the Lac Operon is determined jointly by the levels of glucose and lactose in the cell. Being a monosaccharide, glucose is easier (i.e., takes less energy) to digest; therefore, if glucose is present, the cell will prefer to use it as an energy source. However, if glucose is not available as an energy source, the cell will use lactose instead. A table describing this relationship is below:
Glucose/Lactose Relationship to Lac Operon Transcription (2)
Carbohydrates
CAP-cAMP Complex
LacI Repressor
RNA Polymerase
Transcription of Lac Operon
+ Glucose, + Lactose
Not bound to DNA
Lifted off operator site
Keeps falling off promoter site
Very low transcription
Cell 2
Cell 3
From this table, we can observe a multitude of things:
see that transcription of the Lac Operon occurs only when the cell is in the presence of lactose, but not glucose. To digest lactose, the cell needs β-galactosidase, which can only be produced by initiating transcription of the Lac Operon.
POSITIVE REGULATION: The LacI Repressor
Explain here
NEGATIVE REGULATION: CAP-cAMP Complex
Explain here
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Design: Our genetic circuit
OUR GENE SWITCH:
Building: Assembly Scheme
Testing: Modeling and GFP Imaging
A LAC SWITCH MODEL
We used a previously published synthetic switch, developed by Ceroni et al., to understand how our system could potentially be modeled and simulated.
AN INTERACTIVE MODEL
We used a model of the natural Lac operon to understand how changing the parameter values changes the behavior of the system.
COLLECTING IMPERICAL VALUES TO IMPROVE THE MODEL
We explored how one technique, imaging via microscopy could be used to determine the production rate of an output protein, in this case GFP in yeast, could be used to determine a "real" value for maximum GFP production rate under our own laboratory conditions.
Ideally, the GFP production rate measured by this method could be entered as a value for [which parameter] in the Ceroni et al. model.
Human Practices
Our Team
My name is Shay Ravacchioli, and I am a Junior majoring in Biomedical Engineering with minors in Biological Sciences and Psychology. I am taking BME 494 because I think Synthetic Biology is fascinating. An interesting fact about me is that I play piano and guitar.
My name is Jenessa Lancaster, and I am a Junior majoring in Biomedical Engineering with a minor in Psychology. I am taking BME 494 because I have always wanted to learn more about Synthetic Biology and Genetic Engineering. An interesting fact about me is that I write songs.
My name is ###, and I am a ### majoring in ###. I am taking BME 494 because ###. An interesting fact about me is that ###.
My name is ###, and I am a ### majoring in ###. I am taking BME 494 because ###. An interesting fact about me is that ###.
Works Cited
[1] Heller, H. Craig., David M. Hillis, Gordon H. Orians, William K. Purves, and David Sadava. Life: The Science of Biology. Sunderland, MA,: Sinauer Ass., W.H. Freeman and, 2008. N. pag. Print.
[2] Escalante, Ananias. "Regulation I." Class Notes. University of Arizona. 20 February 2013.