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if you add a timer to produce the advance signal, it will be a clock

This uses only cas9 repressors and a small molecule signal to handle states.

Key:
-> constitutively active promoter
n:binding site for cas-9 repressor for nth node, allows transcription without cas9
n':binding site for cas-9 repressor for nth node, allows transcription without cas9
A: (code for advance) some system so that A must be present for transcription
(n) and (n'): codes for guide rna that binds to n or n' to stop transcription there
payload: the reporter for a node, each node will have a different one so you can see state, each node will probably have a different fluorescent protein.
, breaks up units of transcription regulators and gene expression, each unit between commas is a promoter, the appropriate regulators, and the expressed molecule

each line is a node

circuit of nodes (there isn't supposed to be a cross out, I don't know why its there)

->0'(1),0 payload,>0(3'),>0(3),->A0(0')

->1'(2),1 payload,>1(0'),>1(0),->A1(1')

->2'(3),2 payload,>2(1'),>2(1),->A2(2')

->3'(0),3 payload,>3(2'),>3(2),->A3(3')

explanation of components (same comma convention):
normally blocks next node,payload is on when node active, previous nodes blocking blocked when node active so a node activates itself, node blocks previous node for state transitions, node blocks blocking of next node when active and activator present which causes next node to turn on also for state transitions.

future state changes:  each addition of (A) will move state forward one slot
for an active stage n, (A) causes n+1 to be active, so both n and n+1 are active, then n+1 causes n to be inactive, so n+1 is the only active state.
all nodes are inactivated by the previous node except the active one.

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Applications:

Time progression, biological clock.

Any multi-step chemical/biological process moderated by a single organism.Beer brewing.

Ethanol/Biofuel production.

Drugs/Enzyme production.

Chemical processes with steps that would normally interfere with one another moderated locally.

Safety precaution, self-termination.

Biological CS circuits. Large AND and OR Gates

Add back command to create Turing Machine.

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Implementation:

Cas9, Guide RNA for repression.

mRNA sensing repression.

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