All the following statements are correct, except:

Options

A. Retrovirus is commonly used as a vector for introducing a DNA fragment in human lymphocytes.
B. In India, the organisation responsible for assessing the safety of introducing genetically modified organisms oor public use is GEAC.
C. The correct order of steps in polymerase chain reaction is denaturation , extension and annealing.
D. The DNA fragments separated on an agarose gel can be visualized after staining with ethidium bromide.

Answer

To solve the question, we need to identify the incorrect statement among the provided options. Let's analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** Retrovirus is commonly used as a vector for introducing a DNA fragment in human lymphocytes.

**Analysis:** This statement is correct. Retroviruses are indeed used in gene therapy to introduce genetic material into human cells, including lymphocytes.

### Step 2: Analyze the second statement
**Statement:** In India, the organization responsible for assessing the safety of introducing genetically modified organisms for public use is GEAC.

**Analysis:** This statement is also correct. The Genetic Engineering Appraisal Committee (GEAC) is responsible for the approval and regulation of genetically modified organisms in India.

### Step 3: Analyze the third statement
**Statement:** The correct order of the steps in polymerase chain reaction (PCR) is denaturation, extension, and annealing.

**Analysis:** This statement is incorrect. The correct order of steps in PCR is denaturation, annealing, and then extension. Therefore, this statement is the one that is incorrect.

### Step 4: Analyze the fourth statement
**Statement:** The DNA fragment separated on an agarose gel can be visualized after staining with ethidium bromide.

**Analysis:** This statement is correct. Ethidium bromide is a common dye used to stain DNA in agarose gels, allowing visualization under UV light.

### Conclusion
After analyzing all the statements, the incorrect statement is the third one regarding the order of steps in PCR.

### Final Answer
The incorrect statement is: **The correct order of the steps in polymerase chain reaction is denaturation, extension, and annealing.**

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