Which instrument is commonly used to separate DNA by size in gene engineering workflows?

Which instrument is commonly used to separate DNA by size in gene engineering workflows?

• A. Mass spectrometry
• B. Gel electrophoresis
• C. Centrifuge
• D. pH meter

Answer: (B)

DNA separation by size is accomplished with a gel electrophoresis setup. In this technique, DNA fragments are loaded into a porous gel (typically agarose) and an electric field is applied. Because DNA has a negative charge from its phosphate backbone, fragments migrate toward the positive electrode. The gel matrix slows larger fragments more than smaller ones, so smaller pieces travel farther and appear as bands at different positions. Running a DNA ladder with known fragment sizes alongside your samples lets you estimate the sizes of your fragments. This method is a staple in gene engineering workflows for checking PCR products, digest fragments, and plasmid constructs, because it directly shows fragment length distribution. Other instruments don’t separate DNA by size in the same way. Mass spectrometry analyzes molecules by mass-to-charge ratio, not by size separation in a gel. A centrifuge separates based on density and sedimentation rates, not by size differences in a gel matrix. A pH meter measures acidity, which has no role in separating DNA fragments.

DNA separation by size is accomplished with a gel electrophoresis setup. In this technique, DNA fragments are loaded into a porous gel (typically agarose) and an electric field is applied. Because DNA has a negative charge from its phosphate backbone, fragments migrate toward the positive electrode. The gel matrix slows larger fragments more than smaller ones, so smaller pieces travel farther and appear as bands at different positions. Running a DNA ladder with known fragment sizes alongside your samples lets you estimate the sizes of your fragments. This method is a staple in gene engineering workflows for checking PCR products, digest fragments, and plasmid constructs, because it directly shows fragment length distribution.

Other instruments don’t separate DNA by size in the same way. Mass spectrometry analyzes molecules by mass-to-charge ratio, not by size separation in a gel. A centrifuge separates based on density and sedimentation rates, not by size differences in a gel matrix. A pH meter measures acidity, which has no role in separating DNA fragments.