Which of the following laboratory techniques utilizes an electric current and relies on the fact that DNA molecules are negatively charged?
A) PCR
B) gel electrophoresis
C) restriction enzymes
D) DNA isolation
Answer (2)
The correct answer is B) gel electrophoresis , which uses an electric current to separate DNA fragments based on their size due to their negative charge. In this technique, DNA moves through a gel towards a positive electrode. It is widely used for various genetic analyses.
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The correct answer to the question is B) gel electrophoresis.
Gel electrophoresis is a laboratory technique used to separate mixtures of DNA, RNA, or proteins according to molecular size. The molecules to be separated are pushed by an electrical field through a gel that contains small pores.
Here's how it works step-by-step:
Preparation : A gel (often made of agarose) is poured into a tray and allowed to set. Wells are created in the gel where the samples will be placed.
Loading the Samples : DNA samples, mixed with a loading dye for visibility, are placed into the wells in the gel.
Applying the Electric Current : The gel is placed in a buffer solution and an electric current is applied. DNA molecules are negatively charged due to their phosphate backbone, so they are attracted to the positive electrode.
Separation : As the DNA molecules move, smaller fragments travel faster through the gel's pores than larger ones. This separates the DNA fragments according to size.
Visualization : After the run, the DNA in the gel is treated with a stain that binds to DNA and fluoresces under UV light, allowing the separation pattern to be visible.
Gel electrophoresis is useful in various kinds of analysis, including genetic fingerprinting, assessment of PCR products, and checking the quality or integrity of DNA samples. It relies essentially on the fact that DNA is negatively charged and will migrate towards the positive pole when an electrical field is applied.
