Which of the following statement is correct:-

Options

A. DNA is synthesized through out the cell-cycle
B. Cell division is inhibited by cytokinin
C. Chromosome are condensed at S - stage
D. Only extra chromosomal DNA is replicated at any stage of cell cycle

Answer

To determine which of the statements is correct, let's analyze each option step by step:

1. **Option 1: DNA is synthesized throughout the cell cycle.**
- This statement is incorrect. DNA synthesis occurs specifically during the S phase (Synthesis phase) of interphase. During other phases of the cell cycle, such as G1, G2, and M, DNA is not being synthesized.

2. **Option 2: Cell division is inhibited by the cytokine.**
- This statement is also incorrect. Cytokines are signaling molecules that can promote or influence cell division rather than inhibit it. They play a role in regulating the cell cycle and can stimulate cell division.

3. **Option 3: Chromosomes are condensed at S stage.**
- This statement is incorrect. Chromosomes are not condensed during the S phase; they are replicated during this phase. Chromosome condensation occurs during prophase of mitosis when the cell is preparing to divide.

4. **Option 4: Only extra chromosomal DNA is replicated at any stage of the cell cycle.**
- This statement is correct. Extra chromosomal DNA, such as plasmids in bacteria or mitochondrial DNA, can be replicated at various stages of the cell cycle, not just during the S phase.

**Conclusion:**
The correct statement is **Option 4: Only extra chromosomal DNA is replicated at any stage of the cell cycle.**

---