Biological Equivalence Problem

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Dealing with biological equivalence

Mathematically, the permutations (1,2) and (-2,-1) are not hard to distinguish. However, in a biological system, these two are indistinguishable. Transcription can occur in either direction (either the plus strand or minus strand) as long as the promoter is facing towards the coding region. A promoter followed by RBS-Tet (1,2) and a reversed RBS-Tet followed by a reversed promoter (-2,-1) will both be expressed (tetracycline resistant). Colonies carrying either of these configurations will grow on media containing tetracycline (as illustrated below). Thus, (1,2) and (-2,-1) are biologically equivalent.

Equivalence1.gif


To be able to distinguish the two permutations, we generated a reverse RFP reporter () to be placed as a stationary unit to the left of the pancake stack. In any configuration of pancakes where the promoter is in the reverse orientation, the cells will express RFP and glow red.

Equivalence2.gif

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