Mary performs a PCR reaction and runs it on an agarose gel, using 100-bp ladder
ID: 187481 • Letter: M
Question
Mary performs a PCR reaction and runs it on an agarose gel, using 100-bp ladder as her molecular weight standard. She images the gel using UV light and sees NO bands (no band in her PCR reaction and no bands for her ladder). Which of the following could explain these results? Explain each answer.
1. Mary forgot to add Gel Red when pouring the gel.
2. Mary's PCR product had an unusually high % of G and C bases.
3. Mary connected the electrodes to her gel incorrectly, swapping the positive and negative poles.
Explanation / Answer
Answer:
Option 1 is correct.
Explanation:
DNA can not be visualized in the visible light.
So, the addition of a dye such as EtBr or Gel red enables the visualization of DNA under UV-transillumination.
The visualization of DNA does not depend upon the GC or AT content of DNA as the gel red or EtBr does not discriminate them.
Even if the electrodes are swapped, she should be able to see DNA bands in the opposite direction.