Cell Cycle Duration Calculator
Calculate the duration of each cell cycle phase (G1, S, G2, M) from labeling experiments. Determine the fraction of cells in each phase and total cell cycle length.
🧬 Cell Biology📐 Tc = Ts / LI (from BrdU labeling)🧬 Biology
Labeling index LI (fraction in S phase)
S phase duration Ts (hours)
Mitotic index MI (fraction in M phase)
Total doubling time Td (hours)
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Cell Cycle Duration Calculator | — | Tc = Ts / LI (from BrdU labeling) | hours |
Step-by-Step Examples
Example 1
BrdU Labeling Experiment
LI = 0.30 (30% cells in S phase). S phase duration Ts = 7 hours.
- Tc = Ts/LI = 7/0.30 = 23.3 hours
- Total cell cycle is about 23 hours
- G1 + G2 + M = 23.3 - 7 = 16.3 hours
✓ Cell cycle Tc = 23.3 hours
Example 2
Mitotic Index
Mitotic index MI = 0.03. Cell cycle = 24 hours.
- M phase = MI x Tc = 0.03 x 24 = 0.72 hours
- About 43 minutes in mitosis
- Typical mammalian cells: 30-60 min in M phase
✓ M phase duration = 0.72 h (43 min)
Example 3
HeLa Cell Phases
Known: Tc = 22 h, Ts = 7 h, TM = 1 h, TG2 = 4 h.
- G1 = 22 - 7 - 1 - 4 = 10 h
- G1 = 10 h (often the most variable phase)
- Typical HeLa: G1~11 h, S~8 h, G2~4 h, M~1 h
✓ G1 = 10 h (variable; regulated by growth factors)
Real-World Applications
Cancer Biology
Cancer cells often have shortened or dysregulated G1 phase. Cell cycle kinetics affect drug response.
Developmental Biology
Different cell types have different cell cycle lengths. Early embryo cells cycle rapidly (< 1 hour); differentiated cells may not divide.
Flow Cytometry
DNA content histogram gives fraction in G1 (2N DNA), S (between 2N-4N), and G2+M (4N DNA).
Drug Development
Checkpoint inhibitors (CDK inhibitors) specifically target cell cycle progression. Kinetics determine drug scheduling.
Common Mistakes to Avoid
⚠️
LI = Ts/Tc only during steady state
The formula assumes the cell population is in exponential growth (all phases populated). Not valid for quiescent or synchronous populations.
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Mitotic index is a proxy, not direct duration
MI = Tm/Tc in exponential growth. But collecting figures must be used carefully if synchronization is incomplete.
⚠️
S phase detected by BrdU or EdU
BrdU (bromodeoxyuridine) or EdU incorporate into DNA during S phase. After labeling, immunostaining detects S-phase cells.
Frequently Asked Questions
What are the phases of the cell cycle? ▾
G1 (gap 1): cell growth, preparation. S (synthesis): DNA replication. G2 (gap 2): preparation for division. M (mitosis): nuclear division. G0: quiescent (out of cycle).
What are cell cycle checkpoints? ▾
G1/S checkpoint: checks for DNA damage and growth signals before S phase. G2/M checkpoint: checks DNA replication completed. Spindle assembly checkpoint: all chromosomes attached before separation.
What are CDKs? ▾
Cyclin-dependent kinases (CDKs) are enzymes that phosphorylate target proteins to drive cell cycle progression. CDK4/6-cyclin D drives G1. CDK2-cyclin E drives S entry. CDK1-cyclin B drives M phase.
How do cancer drugs target the cell cycle? ▾
CDK4/6 inhibitors (palbociclib): block G1 progression. Taxanes: prevent spindle depolymerization, blocking M phase. Hydroxyurea: inhibits ribonucleotide reductase, blocking S phase.
What is contact inhibition? ▾
Normal cells stop dividing when they contact each other (due to serum factor depletion and cadherin contacts). Cancer cells lose contact inhibition and continue dividing at high density.