Transcript for the LearnGenetics Simulation
Slide 1
You are holding a small plastic tube with some clear liquid in it.
You’ve been told that the liquic contains DNA strands of several different lengths
Your job is to figure out what those lengths are. How will you do it?
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Slide 2
If the DNA strands were as big as your shoe laces, you could sort them out by
hand into groups and measure them. (Press FORWARD to continue)
Slide 3
But DNA strands are molecules so tiny that you can’t see them even under most
microscopes.
Is there a way to sort and measure DNA strands in your tube even though you
can’t see or touch them?
There is! It’s called gel electrophoresis (pronounced ee-LEK-tro-fo-REE-sis)
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Slide 4
Scientists use gel electrophoresis whenever they need to sort DNA strands
according to length.
This technique is also useful for separating other types of molecules, like protins.
How does this work?
Slide 5
The “gel is the filter that sorts the DNA strands. It’s like a sponge made of Jell-O
with many holes in it.
Slide 6
We place DNA samples into holes at one end of the gel.
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Slide 7
Electrophoresis is how we push the DNA strands through the gel filter
By adding an electrical current, we can make the DNA move.
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Slide 8
Short strands move through the holes in the gel more quickly than long strands.
Over time, the shorter strands in the sample will move farther away from the
starting point than the long er strands. DNA strands of the same length will move
at the same speed and end up grouped together. In this way, the DNA strands in
the sample sort themselves.
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Slide 9
Staining the sorted groups of DNA makes them visible to the naked eye.
Although we can’t see a single DNA strand, we can see large groups of stained
DNA strands.
These groups show up as bands in the gel.
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Slide 10
Now it’s your turn to “run a gel” (That’s scientist slang for gel electrophoresis)
Follow along with the steps shown above!
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Slide 11
Here is what you will need to make a gel.
Powdered agarose, buffer, a flask, a microwave, the gel mold and the gel comb
Making an electrophoresis gel is a lot like making Jell-O. But you don’t want to eat
this type of gel!
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Slide 12 – Getting the gel ready. This is an interactive animation. Tick off when
you have followed each instruction.
Put a small amount of agarose into the flask
Agarose is a dried powder similar to gelatin but made from seaweed
On diagram – click and drag spoon
Add some liquid buffer to the flask.
The buffer is a salt water solution that will let electrical charges flow through the
gel.
We’ve loosely placed plastic wrap over the top of the flask to prevent the liquid
from boiling over.
Open the microwave by pressing the “open button”.
Place the flask containing the buffer and agarose mixture inside the microwave.
Heat the mixture until the agarose melts into the buffer.
We’ve removed the plastic wrap from the top of the flask.
Pour the melted agarose mixture into the mold.
Notice that the mold has tape on each end to hold in the melted agarose
Place the comb into the gel on one end
The notches in the gel mold hold it in place
Let the gel cool and solidify
This usually takes about half an hour, but we’ll speed up the clock for you.
As the gel cools, tiny holes will form in it.
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It goes on but I am getting bored with typing. Pity they didn’t allow copy paste!
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