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. 2006 Feb 1;361(1467):495–506. doi: 10.1098/rstb.2005.1808

Figure 5.

Figure 5

Intrinsic and extrinsic noise. (a, b) Intrinsic noise shows up as the spread of points along the y=−x axis and extrinsic noise causes the spread along the y=x axis. This is because extrinsic noise (alone) causes the two reporters to vary in an identical fashion; any differences between the two reporters (in the same cell) is attributed to intrinsic noise. An E. coli gene at low expression levels. (a) Experimental data reproduced with permission from (Elowitz et al. 2002). The data shows less intrinsic noise for strain M22 than for strain D22. (b) Simulation of the same scenario. (c, d) A yeast gene at high expression levels. (c) experimental data reproduced with permission from Raser & O'Shea (2004). (d) simulation of the same scenario. Here, CFP means cyan fluorescent protein, and YFP means yellow fluorescent protein. In the simulations, ‘CFP’ and ‘YFP’ are just the names given to our two in silico reporter genes.