Chromatin fibres duplication, Genetic material -4C, Histone protein synthesis, Membranous organelle duplication, DNA replication, centriole duplication.
How many of the above features are associated with synthesis phase of cel cycle ?

Options

A. Three
B. Five
C. Four
D. Six

Answer

To determine how many of the listed features are associated with the synthesis (S) phase of the cell cycle, we will analyze each feature one by one:

1. **Chromatin Fibres Duplication**: This process occurs during the S phase as the cell prepares for division by duplicating its genetic material.

2. **Genetic Material - 4C**: The transition from 2C to 4C indicates that DNA replication has occurred, which is a key event in the S phase.

3. **Histone Protein Synthesis**: Histones are proteins that package and order DNA into structural units called nucleosomes. Their synthesis occurs during the S phase to accommodate the newly replicated DNA.

4. **Membranous Organelle Duplication**: This process primarily occurs in the G1 phase and is not a defining feature of the S phase. Some organelle duplication may continue into the G2 phase, but it is not a major characteristic of the S phase.

5. **DNA Replication**: This is the hallmark of the S phase, where the cell's DNA is replicated to ensure that each daughter cell will have a complete set of genetic information.

6. **Centriole Duplication**: While centriole duplication is essential for cell division, it primarily occurs in the S phase, preparing for the formation of the spindle apparatus during mitosis.

Now, let's summarize the association of each feature with the S phase:

- Chromatin fibres duplication: **Yes** (S phase)
- Genetic material - 4C: **Yes** (S phase)
- Histone protein synthesis: **Yes** (S phase)
- Membranous organelle duplication: **No** (primarily G1 phase)
- DNA replication: **Yes** (S phase)
- Centriole duplication: **Yes** (S phase)

Counting the features associated with the S phase, we find that there are **4 features** (Chromatin fibres duplication, Genetic material - 4C, Histone protein synthesis, DNA replication, and Centriole duplication).

### Final Answer:
**4 features are associated with the synthesis phase of the cell cycle.**