1. Interphase:
- G1 Phase: The cell grows and carries out normal metabolic processes.
- S Phase: This is the crucial phase for chromosome preparation. DNA replication occurs, resulting in two identical copies of each chromosome, called sister chromatids. These sister chromatids are held together at a region called the centromere.
- G2 Phase: The cell continues to grow and prepares for mitosis.
2. Chromatin Structure:
- During interphase, the chromosomes exist as long, thin strands of chromatin, which is a complex of DNA and proteins. This structure allows for easy access to the DNA for processes like replication and transcription.
3. Condensation:
- As the cell transitions from interphase to mitosis, the chromatin fibers condense and become much more compact. This process of condensation makes the chromosomes visible under a light microscope.
Essentially, before mitosis, chromosomes go through these key changes:
* Replicate: They duplicate their DNA to ensure each daughter cell gets a complete set.
* Condense: They compact their structure to become more visible and easier to move during cell division.
This process is crucial for ensuring that each new cell receives a complete set of genetic material and can function properly.
