20_180_devices

20_180_devices - 20.180:Devices Summary The material on...

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20.180:Devices Summary The material on this page covers three topics. First, we briefly review how to make different sorts of gene-expression based devices. Second, we develop a simple framework for modeling the behavior of genetic devices. Third, we use the models to estimate some physical characteristics of our devices (for example, device latency). Introduction From before, you know that a genetically encoded inverter (i.e., a Boolean NOT gate) can be made by combining a ribosome binding site (RBS), driving expression of an open reading frame (ORF) encoding a repressor protein, followed by a transcription terminator. The signal is inverted when the repressor protein binds an operator site elsewhere on the DNA, resulting in repression of gene expression from the operator site. Click on Figures 1 and 2 below for more information ( See Comic reference if you need more background information for how genetically encoded inverters work). Figure 1. Parts of an inverter. Figure 2. How to make an inverter. Genetic Devices An inverter is one type of device. We can produce many different types of gene- expression based devices. For example, all sorts of logic gates can be implemented as gene-expression devices. We can also implement other sorts of devices such as sensors, actuators, and even cell-cell communication devices. Simple sketches and explanations of different gene-expression devices are given below. You can make many more types of genetic devices. The important concept to remember is that you want to make devices that allow subsequent hiding of the details for how the device actually works, so that other people can easily use your devices!
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Figure 3a. Gene-expression OR gate. Two standard PoPS input signals enter from the left, driving independent expression of identical copies of a gene encoding an activator protein. The activator turns ON a standard PoPS output signal from the operator site on the right. Figure 3b. Gene-expression NOR gate. Two standard PoPS input signals enter from the left, driving independent expression of identical copies of a gene encoding an repressor protein. The repressor turns OFF a standard PoPS output signal from the operator site on the right. Figure 3c. Gene-expression AND gate. Two standard PoPS input signals enter from the left, driving independent expression of different genes each encoding one half of a heterodimeric activator protein. The heterodimeric activator protein turns ON a standard PoPS output signal from the operator site on the right.
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Figure 3d. Gene-expression NAND gate. Two standard PoPS input signals enter from the left, driving independent expression of different genes each encoding one half of a heterodimeric repressor protein. The heterodimeric repressor protein turns OFF a standard PoPS output signal from the operator site on the right. Figure 3e. Gene-expression SENDER gate. A standard PoPS input signal enters from the
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This note was uploaded on 11/11/2011 for the course BIO 20.010j taught by Professor Lindagriffith during the Spring '06 term at MIT.

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20_180_devices - 20.180:Devices Summary The material on...

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