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Name: Patricie M.
Status: Student
Age: 14
Location: N/A
Country: N/A
Date: March 2004

Dear Scientist,

I have a question about how forensics helps to solve crimes? And how does DNA get broken down into those little lines? I am just wondering, because I am thinking of becoming a forensic scientist someday. If you can help me out with these questions, I would really appreciate it.

DNA is a very long molecule. Each chromosome is actually a long piece of DNA, so you have 46 very long pieces of DNA in each of your cells. It is estimated that each cell contains 3 billion letters of DNA. That's a lot of DNA to analyze all at once. It turns out that bacteria have enzymes that act as DNA cutters; they use them to help prevent viral DNA from inserting itself into the bacteria. These enzymes cut the DNA up into smaller bits. Scientists have learned to use these enzymes to cut DNA up into bits in a test tube. Then these bits can be separated from each other by a process called electrophoresis, which separates the DNA bits, or restriction fragments, by the size of the piece using electricity. Heavier pieces move more slowly and smaller pieces move more quickly. So what you see is a series of lines called bands. Since each person's DNA is unique the places that the enzymes cut are in different places, so the pieces are of different sizes. Therefore, each person's band pattern will be a little different. It is more complicated than this of course, but that is the simple answer.


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