One-stop Guide to Cell Cycle Analysis: From PI/BrdU/EdU to Flow Cytometry/WB/IF

**One**

**Cell Cycle Basics**

During cell proliferation, normal cells undergo a cyclical transition through G1 phase → S phase → G2 phase → M phase in sequence, while quiescent cells enter the non-proliferative G0 phase. The characteristics of each phase and their core regulatory molecules are highly specific, forming the basis for the design of detection techniques.

**Image**

*Classic Cell Cycle Diagram*

**1. Key Characteristics of Each Phase**

- **① G0 Phase**: Quiescent stage, non-proliferative state (e.g., differentiated mature neurons, hepatocytes).

- **② G1 Phase**: Early interphase, DNA content 2N. Cell growth, RNA/protein synthesis. Checks environmental signals, determines whether to enter S phase (Restriction Point).

- **③ S Phase**: DNA synthesis phase. DNA replicates from 2N to 4N.

- **④ G2/M Phase**: DNA content 4N. Checks DNA replication integrity, proceeds to mitosis (M phase: prophase, metaphase, anaphase, telophase, cytokinesis).

**2. Key Regulatory Molecules**

The cell cycle progression is precisely regulated by Cyclin-CDK (Cyclin-Dependent Kinase) complexes, with expression characteristics for each phase as follows:

- ▸ Early G1: Cyclin D + CDK4/6

- ▸ G1/S Transition: Cyclin E + CDK2

- ▸ S Phase: Cyclin A + CDK2

- ▸ G2/M Transition: Cyclin B + CDK1

- ▸ Ki-67: Proliferation marker, low expression in G0, high expression in G1-M.

Abnormal cell cycles are commonly observed in cancer (e.g., G1失控 due to Rb pathway inactivation) and in response to chemotherapeutic drugs (e.g., paclitaxel inducing G2/M arrest).

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**Two**

**Cell Cycle Detection Steps**

Regardless of the specific detection method used, the pre-treatment steps for cell cycle experiments are highly consistent. The core objective is to obtain a single-cell suspension while ensuring cell integrity. The specific process is as follows:

1. **① Cell Culture and Treatment**: Culture cell