Biotechniques | Principles of Gel Electrophoresis (DNA gels)

The video tutorial explains the principles of gel electrophoresis, focusing on DNA gels used to separate DNA molecules by size. It covers the structure of DNA, the mechanism of gel electrophoresis, preparation of agarose gels, and the use of intercalating agents for visualization. The tutorial also discusses interpreting gel results, including estimating DNA fragment sizes using a molecular weight ladder and constructing a standard curve. Finally, it explains how DNA bands are visualized using UV light and intercalating dyes.

What is the primary factor that determines how far a DNA molecule migrates in a gel?

• The color of the gel

• The type of buffer used

• The size of the DNA molecule

• The temperature of the room

In gel electrophoresis, why do DNA molecules move towards the positive electrode?

• Due to the repulsion from the positive electrode

• Because DNA is positively charged

• Because DNA is neutral

• Due to the attraction between negative DNA and the positive electrode

What is the common substance used to make DNA gels?

• Agarose

• Polyacrylamide

• Cellulose

• Starch

Which of the following is a known carcinogen used in DNA gel electrophoresis?

• GelRed

• GelGreen

• TAE buffer

• Ethidium bromide

How does the size of DNA fragments affect their migration distance in a gel?

• Larger fragments migrate further

• Smaller fragments migrate further

• All fragments migrate the same distance

• Size does not affect migration

What is the purpose of a molecular weight ladder in gel electrophoresis?

• To increase the speed of migration

• To provide a size reference for DNA fragments

• To color the gel

• To stabilize the gel

Which method is used to visualize DNA bands in a gel?

• X-ray

• Visible light

• Ultraviolet light

• Infrared light

What is the role of intercalating dyes in gel electrophoresis?

• To make the gel more porous

• To change the gel's color

• To intercalate between DNA strands and fluoresce under UV light

• To increase the gel's thickness

Why might a lab choose GelRed or GelGreen over ethidium bromide?

• They are cheaper

• They are not carcinogenic and more sensitive

• They are more carcinogenic

• They are less sensitive

What is the purpose of constructing a standard curve in gel electrophoresis?

• To increase the gel's conductivity

• To change the gel's pH

• To determine the exact size of DNA fragments

• To make the gel more transparent