Understanding the Cell Cycle
The cell cycle consists of several phases that a cell goes through to grow and divide. The main phases are Interphase, M-phase (mitosis), and the S-phase (synthesis phase).

What is Interphase?
- Interphase is the longest phase of the cell cycle, accounting for approximately 90% of the total cycle duration.
- It comprises three sub-phases:
- **G1 Phase (Gap 1)**: The cell grows and synthesizes proteins necessary for DNA replication.
- **S Phase (Synthesis)**: The cell replicates its DNA, resulting in two copies of each chromosome.
- **G2 Phase (Gap 2)**: The cell continues to grow and prepares for mitosis.

Why is Interphase the Longest?
- **Cell Growth and Preparation**: Interphase is crucial for cellular growth and the preparation needed for division. Cells spend significant time ensuring they are ready to undergo mitosis.
- **DNA Replication**: The S phase involves the replication of genetic material, which is vital for maintaining genetic integrity.
- **Quality Control**: Interphase allows cells to check for DNA damage and repair it before proceeding to division, ensuring healthy cell proliferation.

Comparing with Other Phases
- **M-phase**: This phase is relatively short, lasting only a few hours, as it involves the actual division of the cell.
- **Leptotene**: A sub-phase of prophase I in meiosis, is also not a standalone phase of the cell cycle.
- **S-phase**: While important, it is only a part of Interphase and does not encompass the full preparation and growth activities.
In conclusion, Interphase is the longest phase of the cell cycle, ensuring that cells are adequately prepared for replication and division.