Given below are four statements pertaining to separa- tion of DNA fragments using gel electrophoresis. Iden- tify the incorrect statements.
(a) DNA is negatively charged molecule and so it is loaded on gel towards the Anode terminal
(b) DNA fragments travel along the surface of the gel whose concentration does not affect movement of DNA.
(c) Smaller the size of DNA fragment larger is the dis- tance it travels through it.
(d) Pure DNA can be visualized directly by exposing UV radiation.
Choose correct answer from the options given below

Options

A. (a), (c) and (d)
B. (a), (b) and (c)
C. (b), (c) and (d)
D. (a), (b) and (d)

Answer

To identify the incorrect statements regarding the separation of DNA fragments using gel electrophoresis, let's analyze each statement step by step:

### Step 1: Analyze Statement (a)
**Statement:** DNA is negatively charged molecule and so it is loaded on gel towards the Anode terminal.

**Analysis:** This statement is incorrect. DNA is indeed negatively charged, but it is loaded into the gel towards the cathode (the negative terminal). Under an electric field, DNA will migrate towards the anode (the positive terminal). Therefore, this statement is false.

### Step 2: Analyze Statement (b)
**Statement:** DNA fragments travel along the surface of the gel whose concentration does not affect movement of DNA.

**Analysis:** This statement is also incorrect. The concentration of the gel (typically agarose) does affect the movement of DNA fragments. A higher concentration of gel creates smaller pores, which can impede the movement of larger DNA fragments. Thus, this statement is false.

### Step 3: Analyze Statement (c)
**Statement:** Smaller the size of DNA fragment larger is the distance it travels through it.

**Analysis:** This statement is correct. In gel electrophoresis, smaller DNA fragments can navigate through the gel matrix more easily than larger fragments, allowing them to travel further. Therefore, this statement is true.

### Step 4: Analyze Statement (d)
**Statement:** Pure DNA can be visualized directly by exposing UV radiation.

**Analysis:** This statement is incorrect. Pure DNA cannot be visualized directly under UV light; it must be stained with a dye (like ethidium bromide) that binds to the DNA. Only after staining can the DNA be visualized under UV light. Therefore, this statement is false.

### Conclusion
The incorrect statements are:
- (a) DNA is negatively charged molecule and so it is loaded on gel towards the Anode terminal.
- (b) DNA fragments travel along the surface of the gel whose concentration does not affect movement of DNA.
- (d) Pure DNA can be visualized directly by exposing UV radiation.

### Final Answer
The correct answer is option 4: A, B, and D are incorrect statements.

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