A gel electrophoresis is performed, but when the gel imager is used, no bands appear. The researcher might have forgotten to

Question

A) add electric current.
B) add antibody.
C) ligate the DNA fragments together.
D) include DNA dye.
E) include an RNA probe.

Answer 1

A, D

Clarify Question
• What is the key concept addressed by the question?
        o This question addresses the gel electrophoresis technique.
• What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.
• What key words does the question contain and what do they mean?
        o Gel electrophoresis is a technique to separate DNA fragments by size.
        o The bands represent the different size pieces of DNA. 

Gather Content
• What do you already know about gel electrophoresis?
        o Gel electrophoresis uses a soft agarose gel to separate DNA.
        o The DNA is pipetted into wells at one end; then electrical current drags the DNA through the gel.
        o The different sized fragments travel at different speeds, so they separate across the gel.
        o The bands are visualized using a DNA dye. 

Consider Possibilities
• Consider the different answer options. Which can you rule out?
        o Could the researcher have forgotten to add antibody or an RNA probe? No, because those are not used with the simple gel electrophoresis technique.
        o Could the researcher have forgotten to ligate the DNA fragments? No. The point of a gel is to separate DNA fragments, not connect them. 

Choose Answer
• Given what you now know, what information and/or problem-solving approach is most likely to produce the correct answer?
        o The researcher could have forgotten to turn on the electric current-then the DNA would stay in the wells and not separate properly.
        o The researcher could also have forgotten to add the DNA dye-then the DNA would be separated, but the bands would not be visible. 

Reflect on Process
• Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked what could have gone wrong with gel electrophoresis.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that antibodies, RNA probes, and membranes are not involved with simple gel electrophoresis?
        o Did you realize that gel electrophoresis requires electric current, and a DNA dye?