What is Gel Electrophoresis | Don't Memorise

Summary

This script delves into the fundamental technique of gel electrophoresis, a method used to separate DNA molecules by size. It explains the process, starting from the negatively charged DNA's movement in an electrical field through an agarose gel, to the use of ethidium bromide for visualization under UV light. The script also covers the use of DNA ladders for size determination and the extraction of specific DNA fragments for further analysis, highlighting gel electrophoresis as a crucial tool in recombinant DNA technology.

Takeaways

• 🌟 Gel electrophoresis is a technique used to separate DNA molecules based on their size.
• 🔍 The term 'gel electrophoresis' comes from the use of an electrical field in a gel medium to separate charged molecules.
• 🚀 DNA molecules are negatively charged due to the phosphate groups in their backbone, which facilitates their movement in the gel.
• 🌊 Agarose gel, derived from seaweed, is commonly used as the medium for DNA separation.
• 🔬 The separation principle is analogous to a sieve, where smaller particles pass through more easily than larger ones.
• 🧬 DNA samples with different sized fragments are loaded into wells in the gel for the electrophoresis process.
• 🔋 An electric field is applied, causing the negatively charged DNA fragments to move towards the positive anode.
• 🎨 A colored loading dye is used to visualize the movement of DNA through the gel, as DNA itself is colorless.
• 🌈 Ethidium bromide is used to stain the DNA, allowing the separated fragments to be seen under ultraviolet light as orange bands.
• 📏 The size of the DNA fragments can be determined by comparing the position of the bands to a DNA ladder.
• 🔬 The process of cutting out and extracting the desired DNA fragment from the gel is known as 'excision' and is used for further analysis.

Q & A

What is gel electrophoresis?

Gel electrophoresis is a technique used to separate different DNA molecules based on their sizes by applying an electrical field in a gel medium.

Why is the technique called 'gel electrophoresis'?

The term 'gel electrophoresis' comes from the fact that the separation of DNA molecules occurs within a gel medium under the influence of an electrical field.

What charge do DNA molecules carry?

DNA molecules are negatively charged due to the presence of phosphate groups in their backbone, which are negatively charged.

What type of gel is commonly used for DNA separation in gel electrophoresis?

Agarose gel, which is obtained from seaweeds, is commonly used for DNA separation in gel electrophoresis.

How does the size of DNA fragments affect their movement in the gel?

Smaller DNA fragments move faster through the gel's pores, while larger fragments find it more difficult to move and lag behind due to the size of the pores and their own size.

What is the purpose of using a comb to create wells in the gel?

The comb is used to create wells in the gel to load the DNA samples, allowing for the separation of DNA fragments when the electric field is applied.

Why are the wells for loading DNA samples formed near the cathode?

The wells are formed near the cathode because the negatively charged DNA fragments will move towards the positively charged anode when the electric field is applied.

What is the role of the colored loading dye in gel electrophoresis?

The colored loading dye is used to track the movement of the DNA through the gel, as DNA is colorless. It travels slightly faster than the DNA segments, indicating their progress.

How is the separated DNA visualized after electrophoresis?

The separated DNA is visualized by treating the agarose gel with ethidium bromide, which binds to the DNA and fluoresces under ultraviolet light, revealing bright orange bands representing the DNA fragments.

How can the size of the DNA fragments be determined after separation?

The size of the DNA fragments can be determined by comparing the positions of the bands on the gel with a standard DNA ladder, which provides a reference for fragment sizes.

What is the process called when the desired DNA fragment is cut out from the gel and extracted?

The process of cutting out and extracting the desired DNA fragment from the gel is called 'excision', and the extracted DNA can be used for further downstream processing.