Human Gene Electrophoresis
How does gel electrophoresis separate DNA fragments?
An electric current separates different-sized molecules in a sponge-like matrix because the molecules go towards whichever pole is the opposite charge of their own. The smaller, lighter molecules move through the gel's pores more easily than the large heavy molecules, therefore going further.
Why are DNA and RNA negatively charged?
Because the phosphate groups in their sugar-phosphate backbones contain oxygen, which is negatively charged.
What is the purpose of adding "tracking" dye to the samples?
Being able to clearly see the samples makes it easier to load them into the wells of the gel, and to visibly track the sample's movement through the gel.
By which two qualities does electrophoresis separate substances?
By weight and charge.
What is the purpose of Ethidium bromide in gel electrophoresis?
It stains the DNA by bonding to the DNA's double helix, and it glows under ultraviolet light. This allows resesarchers to see where the separated DNA fragments end up.
What are markers, and why are they used when running the fragments through the gel?
Markers are DNA fragment of known sizes which can be used to determine the size of any DNA fragment by comparison.
What do the black and red ends of the chamber signify?
The black end is the negative end, and the red is the positive end.
Why is a buffer added to the gel?
The buffer prevents fluctuations in the gel's pH and prevents the gel from drying out.
What would happen to the dyes in the gel if the chamber were left on all day?
The dyes would move out of the gel bed and go into the buffer.
If you were to load a sample of known charge into a gel, where would the well have to be located and why?
The well would have to be located on the side that matches the charge of the sample, because the sample will move towards the end of opposite charge.
What would happen if DNA and RNA were both placed in the same well and run on a gel?
They would both move towards the positive end, but the mixture would separate b/c they would travel at different speeds. The RNA would move ahead of the DNA.
If different samples are all put into the same well, what would happen?
They would separate, since some would move faster and others would move slower through the gel.