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DNA Gel Electrophoresis separates fragments of DNA based on size.
DNA Gel Electrophoresis separates fragments of DNA based on size.
Before the gel is used, the DNA from different sources is cut up into fragments using an enzyme that only cuts when it finds a specific sequence of nucleotides (GCAT). These enzymes are called restriction enzymes and there are several types--each with its own sequence at which it cuts.
The main idea of DNA electrophoresis is that every individual has a unique sequence of DNA letters-more than a million are different in each person. Since the code is different, the enzymes will cut each person's DNA in different spots.
DNA Electrophoresis process:
DNA Electrophoresis process:
Step 1: Treat all DNA samples with the same restriction enzyme.
Step 2: Fill wells of gel with DNA samples.
Step 3: Turn on electricity, which pulls negatively-charged DNA through gel at different rates towards the positive terminal. The smaller the fragment, the faster it moves through the gel.
Step 4: Compare the patterns produced in each lane of the gel. The pattern is referred to as a DNA Fingerprint.
Uses for DNA Fingerprinting:
Uses for DNA Fingerprinting:
The patterns of DNA fragments that appear after running a gel electrophoresis are used to compare DNA from two different sources. The sources being compared could be from the same species, or different species. The more fragments that the sources have in common, the more closely related they are. Here are some applications of this technology:
- Determining hereditary relationships like a paternity test. A child will share 50% of its DNA fragments with each parent.
- Obtaining evidence from a crime scene to prove that a suspect was present.
- Comparing different species in order to determine evolutionary relationships
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