The synthesis of spindle proteins called as tubulin occurs during

Options

A. `G_(1)`-phase
B. S-phase
C. `G_(2)`-phase
D. M-phase

Answer

To determine during which phase of the cell cycle the synthesis of spindle proteins called tubulin occurs, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Cell Cycle Phases**: The cell cycle consists of four main phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis).

2. **Analyze the G1 Phase**: In the G1 phase, the cell grows and duplicates its organelles and proteins, but DNA replication does not occur. There is no synthesis of spindle proteins during this phase.

3. **Examine the S Phase**: The S phase is primarily focused on DNA replication. Each chromosome is duplicated, but spindle proteins are not synthesized during this phase.

4. **Look into the G2 Phase**: The G2 phase follows the S phase and is another growth phase. It is during this phase that the synthesis of tubulin, which is a key component of spindle fibers, occurs. This is crucial for the formation of the mitotic spindle that will separate chromosomes during mitosis.

5. **Consider the M Phase**: The M phase is where mitosis occurs, leading to the division of the cell into two daughter cells. However, the synthesis of spindle proteins does not occur during this phase; instead, they are utilized for chromosome separation.

6. **Conclusion**: Based on the analysis, the synthesis of spindle proteins (tubulin) occurs during the G2 phase of the cell cycle.

### Final Answer:
The synthesis of spindle proteins called tubulin occurs during the **G2 phase**.

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