2.3.1 Interphase

Key Features of Interphase:

1. Cell Growth:

• The cell increases in size.
• Proteins and organelles are synthesised to support the division process.

2. Replication:

• DNA replication occurs, ensuring each daughter cell will have an identical copy of genetic material.
• This results in the formation of sister chromatids, which are joined at the centromere.

3. Preparation for Division:

• Chromosomes begin to condense, becoming visible under the microscope in later stages of interphase.
• Energy stores (e.g., ATP) are increased to fuel cell division.

Stages of Interphase:

1. G₁ Phase (First Gap Phase):

• The cell grows and performs its normal functions.
• Organelles such as mitochondria and ribosomes are replicated.
• The cell ensures it has sufficient nutrients and energy to proceed.

2. S Phase (Synthesis Phase):

• DNA is replicated, producing identical copies for division.
• Each chromosome now consists of two sister chromatids.

3. G₂ Phase (Second Gap Phase):

• The cell continues to grow and prepare for mitosis.
• Final checks are carried out to ensure there is no damage to the DNA.
• Enzymes and proteins required for division are produced.

Summary of Interphase:

• G₁ Phase: Growth and preparation for DNA replication.
• S Phase: DNA replication.
• G₂ Phase: Final growth and preparation for mitosis.

Importance of Interphase:

• Ensures the cell is properly prepared for division.
• Guarantees that genetic material is accurately replicated, reducing the risk of mutations.