LAMBDA: LYSIS OR LYSOGENY?

1. Phase I: Lambda tries to get its foot in the door.
   1. Recognition of the role of statistical mechanics
   1. Transcriptase starts reading at both P_L and P_R
   2. Transcriptase gets derailed at t_L1 and t_R1 with 80% and 50% efficiencies, respectively, and some reads through to t_L2 and t_R2.
   3. During this process, N and cro are made
   4. Usually N builds up a bit faster than cro.
   5. N negates the effect of t_L1 and t_R1 probably by modifying transcriptase (N's anti-termination is 'before site'.)

2. Phase II: Lambda makes its decision about lysis or lysogeny.
   1. Transcriptase reads leftwards making cIII; and rightwards making cro, O, P, and Q.
   2. cro blocks (represses) P_L and P_R.
   3. Usually Q has built up fast enough to allow the lytic Right-functions to proceed leading to lysis of the cell within 50 minutes. (Q's anti-termination is 'on-site')

3. Phase III: But if Q does not build up enough.
   1. cII and cIII modify Transcriptase such that it now recognizes P_RM and P_RE
   2. Transcriptase reads from P_RE, and reads back over cro and P_R and makes cI (cI = "lambda repressor")
   3. Transcriptase reads from P_RM and establishes the lysogenic Left-functions.

4. Phase IV: Maintaining lysogeny over many generations
   1. cI triply inhibits each P_L and P_R
   2. As the cells divided and cell volume increases, [cI] decreases
   3. Some asymmetric derepression of P_R occurs
   4. Transcriptase recognizes P_RM and reads leftward making more cI.
      (P_RM = promoter for repressor maintenance)

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