What is not true about cell cycle ?
a. During `G_(1)` phase there is active synthesis of RNA and proteins but no change in its DNA content
b. In synthesis or S phases, each chromosome carriers a duplicate set of genes
c. During `G_(2)` phase, a cell contains double the amount ($C) of DNA present in the original diploid cell (2C)
d. In S-phase a cell doubles the original diploid (2n) chromosome number

Options

A. c & d
B. b & c
C. d only
D. b, c & d

Answer

To determine which statement about the cell cycle is not true, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Option A**: "During G1 phase there is active synthesis of RNA and proteins but no change in its DNA content."
- **Analysis**: This statement is true. During the G1 phase, the cell is growing and synthesizing RNA and proteins, but DNA replication has not yet occurred, so the DNA content remains the same.

2. **Option B**: "In synthesis or S phases, each chromosome carries a duplicate set of genes."
- **Analysis**: This statement is also true. During the S phase, DNA replication occurs, resulting in each chromosome being duplicated, which means each chromosome now carries a duplicate set of genes.

3. **Option C**: "During G2 phase, a cell contains double the amount (C) of DNA present in the original diploid cell (2C)."
- **Analysis**: This statement is true as well. After the S phase, during the G2 phase, the cell has completed DNA replication and contains double the amount of DNA compared to the original diploid state.

4. **Option D**: "In S-phase a cell doubles the original diploid (2n) chromosome number."
- **Analysis**: This statement is not true. In the S phase, the cell does not double the chromosome number; instead, it replicates each chromosome, so the number of chromosomes remains the same (2n), but each chromosome now consists of two sister chromatids.

### Conclusion:
The statement that is not true about the cell cycle is **Option D**.

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