Table 2.

Simulated cell-cycle properties of mutant fission yeast strains

Strain	Parameter changes*	Mass at birth (relative)	G1† (min)	S† (min)	G2† (min)	M† (min)	Comment
WT	—	1.00	38	17	78	17
wee1ts	VWee = 0.08	0.48	72	18	31	29
wee1Δ	VWee = V′Wee = 0	0.48	73	18	29	30
mik1Δ	VMik1 = V′Mik = 0	0.98	39	18	73	20
mik1Δwee1ts	VMik1 = V′Mik = 0, VWee = 0.08	No balanced growth, S and M overlap					cut phenotype
pyp3Δ	VPyp = 0	1.08	36	18	79	17
cdc25ts or cdc25Δ	V25 = 0.05, V′25 = 0.00025 or V25 = V′25 = 0	—	—	—	∞	—	G2 block
wee1tscdc25Δ‡	VWee = 0.08, V25 = V′25 = 0	1.22/1.08	22/23	17/17	42/107	31/23	Quantized cycles
wee1tscdc25Δpyp3Δ	VWee = 0.08, V25 = V′25 = 0, VPyp = 0	—	—	—	∞	—	G2 block
mik1Δwee1tscdc25Δ	VMik1 = V′Mik = 0, VWee = 0.08, V25 = V′25 = 0	No balanced growth, S and M overlap					cut phenotype
wee1tscdc25ts	VWee = 0.08, V25 = 0.05, V′25 = 0.00025	0.80	37	17	69	27
wee1Δcdc25Δ	VWee = V′Wee = 0, V25 = V′25 = 0	0.76	40	18	65	27
rum1Δ	k5 = 0	0.99	31	17	84	18
rum1Δwee1ts	k5 = 0, VWee = 0.08	0.41	24	18	77	31	Not viable§
ste9Δ or cdc13dbΔ	V2 = V2c = 0	0.84	12	18	102	18
ste9Δwee1ts	V2 = V2c = 0, VWee = 0.08	0.30	1	18	98	33	Not viable§
ste9Δrum1Δ	V2 = V2c = 0, k5 = 0	0.82	12	18	102	18
ste9Δrum1Δwee1ts	V2 = V2c = 0, k5 = 0, VWee = 0.08	0.28	0	19	98	33	Not viable§

^*Parameter changes relative to the WT set (Table 1) are indicated. 

^† The duration of the appropriate cell cycle phase is given. M phase is initiated when MPF crosses 0.5 from below and it finishes 5 min after MPF_a/PP drops below 0.5. The rules for the onset and completion of S phase are described in Table 1. 

^‡ As a consequence of the quantized cycles, these cells do not behave uniformly. Mean values of cells having the short cycle and the longer cycle, respectively, are separated by/. In the long cycle, during the 107-min G₂ phase, there is a short period with high MPF, probably indicating an early M-like state (see text). 

^§ Cells significantly smaller than a wee1⁻ mutant are considered too small to be viable.