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, let's analyze each statement one by one:

### Step 1: Analyze Statement (i)
**Statement:** 6 turns of B-DNA has 120 nucleotides.
**Analysis:** In B-DNA, one complete turn consists of approximately 10 to 10.5 base pairs. Therefore, in 6 turns, the number of base pairs would be approximately 60 to 63 base pairs. Since each base pair consists of 2 nucleotides, this results in approximately 120 to 126 nucleotides.
**Conclusion:** This statement is **TRUE**.

### Step 2: Analyze Statement (ii)
**Statement:** In prokaryotes, gene regulation generally occurs at the transcriptional level.
**Analysis:** In prokaryotes, transcription and translation occur simultaneously in the cytoplasm, and gene regulation primarily occurs at the transcriptional level.
**Conclusion:** This statement is **TRUE**.

### Step 3: Analyze Statement (iii)
**Statement:** Operon concept was given by Jacob and Monod while working on yeast.
**Analysis:** The operon concept was proposed by François Jacob and Jacques Monod while they were studying bacteria, specifically E. coli, not yeast.
**Conclusion:** This statement is **FALSE**.

### Step 4: Analyze Statement (iv)
**Statement:** The enzyme required for peptide chain synthesis is a ribozyme in bacteria and lies in the 50S subunit.
**Analysis:** The enzyme responsible for peptide bond formation during protein synthesis in bacteria is indeed a ribozyme called peptidyltransferase, which is part of the 50S ribosomal subunit.
**Conclusion:** This statement is **TRUE**.

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

### Final Count of True Statements
- True statements: (i), (ii), (iv)
- False statements: (iii), (v)
**Total True Statements:** 3

### Answer
The number of true statements is **3**.

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