Question

If you want to estimate the size of a DNA fragment, which technique will you use to visualize the size differences?

1. PCR
2. transformation
3. plasmid isolation
4. restriction digestion
5. gel electrophoresis

Answer 1

To estimate the size of a DNA fragment, gel electrophoresis is the technique used. It involves separating DNA fragments on an agarose gel, where fragment size determines migration speed and position on the gel, allowing for size visualization and estimation.

The correct option is 5.

Step-by-step explanation:

To estimate the size of a DNA fragment and visualize the size differences, the technique used is gel electrophoresis. Agarose gel electrophoresis separates DNA molecules based on size due to the negative charge of DNA. The technique involves:

• Treating DNA with a specific restriction endonuclease to cut the DNA into fragments.
• Separating the DNA fragments by size on an agarose gel under an electric field.
• Visualizing the DNA fragments as bands using a DNA stain such as ethidium bromide, where the position of the bands corresponds to the size of the DNA fragments.

Larger DNA fragments move slower and will be closer to the top of the gel, while smaller fragments will move faster towards the positive side and will be located near the bottom. The size of the DNA fragments can be estimated by comparing them to a DNA ladder, which contains DNA fragments of known lengths.