Two regulators switch each other off. What does the circuit store?

• A toggle: one stable state or the other
• A pulse that always fires once
• Nothing at all

A regulator represses its own gene. What wiring is this?

• Mutual repression
• A feed-forward loop
• Autoregulation

In the lac operon, lactose pulls the repressor off the DNA and frees the digestion genes.

Circle one:   True   False

A target fires briefly when its input switches on, then shuts itself off while input stays high. Which motif fits?

• Negative autoregulation alone
• An incoherent feed-forward loop
• A plain unregulated promoter

A coherent feed-forward loop gets a five second input blip, far shorter than its slow arm needs. What happens?

• The target fires at full strength
• The target stays off because the blip dies first
• The circuit deletes the target gene

Tryptophan is abundant in a bacterial cell. What does the trp operon do?

• It destroys all the DNA in the cell
• It shuts production down through its activated repressor
• It switches on lactose digestion

A student claims a coherent loop must pass every input flicker because both arms activate. What is the error?

• Both arms never exist in real cells
• The claim is exactly right
• The slow arm arrives late, so brief flickers die before the target sees both

An embryo needs a sharp stripe of gene activity that turns on and off on schedule. Which wiring would you propose?

• An incoherent feed-forward loop driving a timed pulse
• A toggle locked permanently on
• Removing all regulators from the gene