Question

UV shadowing is used at times for visualising the DNA. Which of the statements is correct for it?

(a) In this method, the DNA bands are visualized because they fluoresce under UV

(b) The DNA bands won’t fluoresce but will absorb the UV light

(c) It is not suitable for visualizing single stranded molecules

(d) It is less preferred over the use of ethidium bromide

The question was posed to me in an online interview.

My question comes from Gel Electrophoresis, Oligonucleotide  & Microarrays in division Basics of Genetic Engineering of Genetic Engineering

Answer 1

Right answer is (b) The DNA bands won’t fluoresce but will absorb the UV light

The best explanation: In this method, the DNA bands won’t fluoresce but will absorb the UV light. This leads to the formation of a non-fluorescent shadow on the screen. It is suitable for visualising single stranded species because the mode of action is not intercalating as in the case of use of ethidium bromide. It is preferred over it because ethidium bromide is often difficult to remove.