Explain how a sample of DNA obtained from a crime scene can be amplified and how gel electrophoresis works
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The DNA can be amplified using a technique called Polymerase Chain Reaction. This uses the fact that DNA can be replicated with extreme precision to make many copies of the DNA segment obtained.
PAGE, or Polyacrylimide Gel Electrophoresis works by chopping this DNA up into tiny strips at predetermined spots using a cutting protein called a ligase. These little segments can then be separated by applying a current through the gel.
You can get a mental image of how PAGE works this way: Imagine that you have a huge flat board that you nailed thousands of nails into to create a "bed of nails". Now hold this board vertically and drop pices of rope that you cut into varying lengths. Some only 1 cm long, others 3, others maybe 10. You can imagine how the smaller segments would fall farther through the nails than the longer ones. This is how PAGE works. The smaller segments of DNA can travel farther through the gel than the longer segments.
PAGE, or Polyacrylimide Gel Electrophoresis works by chopping this DNA up into tiny strips at predetermined spots using a cutting protein called a ligase. These little segments can then be separated by applying a current through the gel.
You can get a mental image of how PAGE works this way: Imagine that you have a huge flat board that you nailed thousands of nails into to create a "bed of nails". Now hold this board vertically and drop pices of rope that you cut into varying lengths. Some only 1 cm long, others 3, others maybe 10. You can imagine how the smaller segments would fall farther through the nails than the longer ones. This is how PAGE works. The smaller segments of DNA can travel farther through the gel than the longer segments.
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