Question

Which of the following statements are correct with respect to DNA separation, isolation and visualization ?
A. The cutting of DNA is done by molecular scissors.
B. The DNA fragments separate according to their size in an agarose gel, upon electrophoresis.
C. The separated DNA fragments can be seen without staining when exposed to UV light.
D. The separated DNA fragments, when stained with ethidium bromide, can be seen in visible light. Choose the correct answer from the options given below :

• A. B and C only
• B. B and D only
• C. A and B only
• D. A and D only

Hint:

For visualization, remember: EtBr + UV = Orange Bands. You cannot skip either the stain or the specific light source!

Answer 1

The Correct Option is C

Genetic engineering relies on the precise manipulation of DNA. Let's analyze the procedural statements:
• Statement A is Correct: Molecular scissors is the common term used for Restriction Endonucleases, which cut DNA at specific palindromic sequences.
• Statement B is Correct: In gel electrophoresis, DNA fragments (which are negatively charged) move toward the anode. The agarose gel acts as a sieve; hence, the fragments separate based on their size (shorter fragments move faster and farther).
• Statement C is Incorrect: Separated DNA fragments are invisible to the naked eye and cannot be seen under UV light without being stained first.
• Statement D is Incorrect: Even after staining with Ethidium Bromide, DNA cannot be seen in normal visible light. It only becomes visible as bright orange-colored bands when exposed to UV radiation. Since only A and B are factually correct, option (3) is the right choice.