Question
What are the stages of the cell cycle, including G1, S, and G2, and the process of mitosis?
Answers
GPT-4o mini
The cell cycle is a series of phases that a cell goes through as it grows and divides. It consists of interphase, which prepares the cell for mitosis and cytokinesis, as well as the mitotic phase where actual cell division occurs. Here are the main stages of the cell cycle:
### 1. Interphase
Interphase is the longest phase of the cell cycle and is divided into three sub-phases:
- **G1 Phase (Gap 1)**:
- The cell grows in size.
- It synthesizes various proteins and organelles.
- The G1 phase also involves the checkpoint where the cell assesses whether conditions are favorable to proceed to the next phase.
- **S Phase (Synthesis)**:
- DNA replication occurs, resulting in the duplication of the chromosomes.
- Each chromosome is now composed of two sister chromatids.
- **G2 Phase (Gap 2)**:
- The cell continues to grow and prepares for mitosis.
- It synthesizes additional proteins and organelles needed for division.
- A second checkpoint occurs here to ensure all DNA is replicated correctly and that the cell is ready to undergo mitosis.
### 2. Mitotic Phase (M Phase)
The mitotic phase consists of two main processes: mitosis and cytokinesis.
- **Mitosis**: Mitosis is the process of nuclear division and is divided into several stages:
- **Prophase**: Chromatin condenses into visible chromosomes, each consisting of two sister chromatids. The nuclear envelope begins to break down, and the mitotic spindle begins to form.
- **Prometaphase**: The nuclear envelope is completely broken down. Microtubules attach to the kinetochores of the chromosomes.
- **Metaphase**: Chromosomes align at the metaphase plate (the cell's equatorial plane). The spindle fibers are fully developed and attached to kinetochores.
- **Anaphase**: The sister chromatids are pulled apart toward opposite poles of the cell as the spindle fibers shorten.
- **Telophase**: The separated chromatids reach the poles and begin to decondense back into chromatin. The nuclear envelope reforms around each set of chromosomes.
- **Cytokinesis**: This process occurs simultaneously with telophase and involves the division of the cytoplasm, resulting in two genetically identical daughter cells. In animal cells, a cleavage furrow forms, whereas in plant cells, a cell plate forms to separate the two new cells.
After cytokinesis, each daughter cell enters the G1 phase of the next cell cycle, and the cycle begins anew.
### 1. Interphase
Interphase is the longest phase of the cell cycle and is divided into three sub-phases:
- **G1 Phase (Gap 1)**:
- The cell grows in size.
- It synthesizes various proteins and organelles.
- The G1 phase also involves the checkpoint where the cell assesses whether conditions are favorable to proceed to the next phase.
- **S Phase (Synthesis)**:
- DNA replication occurs, resulting in the duplication of the chromosomes.
- Each chromosome is now composed of two sister chromatids.
- **G2 Phase (Gap 2)**:
- The cell continues to grow and prepares for mitosis.
- It synthesizes additional proteins and organelles needed for division.
- A second checkpoint occurs here to ensure all DNA is replicated correctly and that the cell is ready to undergo mitosis.
### 2. Mitotic Phase (M Phase)
The mitotic phase consists of two main processes: mitosis and cytokinesis.
- **Mitosis**: Mitosis is the process of nuclear division and is divided into several stages:
- **Prophase**: Chromatin condenses into visible chromosomes, each consisting of two sister chromatids. The nuclear envelope begins to break down, and the mitotic spindle begins to form.
- **Prometaphase**: The nuclear envelope is completely broken down. Microtubules attach to the kinetochores of the chromosomes.
- **Metaphase**: Chromosomes align at the metaphase plate (the cell's equatorial plane). The spindle fibers are fully developed and attached to kinetochores.
- **Anaphase**: The sister chromatids are pulled apart toward opposite poles of the cell as the spindle fibers shorten.
- **Telophase**: The separated chromatids reach the poles and begin to decondense back into chromatin. The nuclear envelope reforms around each set of chromosomes.
- **Cytokinesis**: This process occurs simultaneously with telophase and involves the division of the cytoplasm, resulting in two genetically identical daughter cells. In animal cells, a cleavage furrow forms, whereas in plant cells, a cell plate forms to separate the two new cells.
After cytokinesis, each daughter cell enters the G1 phase of the next cell cycle, and the cycle begins anew.