How many of the following statement are TRUE ?
(i) 6 turns of B - DNA has 120 nucleotides.
(ii) In prokaryotes , gene regulation generally occurs at transcriptional level.
(iii) Operon concept was given by Jacob and Monod while working on yeast.
(iv) The enzyme required for peptide chain synthesis is a ribozyme in bacteria and lies in 50S subunit.
(v) A small segment of RNA synthesized during replication of DNA is ''Okazaki segment''.

Options

A. 2
B. 3
C. 1
D. 5

Answer

To determine how many of the given statements are true, we will analyze each statement one by one.

### Step-by-step Solution:

1. **Statement (i)**: "6 turns of B-DNA has 120 nucleotides."
- Each turn of B-DNA contains approximately 10 base pairs.
- Therefore, 6 turns would contain:
\[ 6 \text{ turns} \times 10 \text{ base pairs/turn} = 60 \text{ base pairs} \]
- Since each base pair consists of 2 nucleotides, the total number of nucleotides is:
\[ 60 \text{ base pairs} \times 2 = 120 \text{ nucleotides} \]
- **Conclusion**: This statement is **TRUE**.

2. **Statement (ii)**: "In prokaryotes, gene regulation generally occurs at transcriptional level."
- In prokaryotes, gene regulation primarily occurs at the transcriptional level, often through mechanisms such as operons.
- **Conclusion**: This statement is **TRUE**.

3. **Statement (iii)**: "Operon concept was given by Jacob and Monod while working on yeast."
- The operon concept was indeed proposed by Jacob and Monod, but they conducted their research on bacteria, specifically E. coli, not yeast.
- **Conclusion**: This statement is **FALSE**.

4. **Statement (iv)**: "The enzyme required for peptide chain synthesis is a ribozyme in bacteria and lies in the 50S subunit."
- The enzyme responsible for peptide bond formation is called peptidyl transferase, which is indeed a ribozyme located in the 50S subunit of the bacterial ribosome.
- **Conclusion**: This statement is **TRUE**.

5. **Statement (v)**: "A small segment of RNA synthesized during replication of DNA is 'Okazaki segment'."
- Okazaki fragments are short segments of DNA synthesized on the lagging strand during DNA replication, not RNA.
- **Conclusion**: This statement is **FALSE**.

### Summary of True Statements:
- True Statements: (i), (ii), (iv)
- False Statements: (iii), (v)

Thus, out of the 5 statements, **3 statements are TRUE**.

### Final Answer:
**3 statements are TRUE.**