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Биология
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практическая работа
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20 стр.
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01.03.2013
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.doc — Microsoft Word
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Текст работы

                          HOW   “DNA”
TESTING WORKS

The tools for solving rapes and murders
have improved rapidly. Five years ago DNA tests couldn’t link suspects to hair
or semen found on a victim. Today a crime lab can identify unique DNA patterns
in a tiny sample of just 100 to 200 cells. The steps scientists take to
implicate or exonerate suspects:

1)      
Collect biological materials from the crime scene and the suspect under
investigation, such as blood, hair, semen or saliva. Every cell is a unique
library of DNA sequences. The goal is to find out if the forensic and suspect’s
samples match.

2)      
Isolate pure DNA by mixing the sample with chemicals that break down other
cellular material. DNA molecules consists of paired filaments that interlock
like zippers, and each filament is made up of chemicals “bases” (A, C, T and G)
aligned in unique sequences.

3)      
Amplify the DNA by separating paired filaments and mixing them with short
fragments known as primers. When a primer locks onto a particular site on a
sample DNA molecule, it triggers production of a longer fragment that matches a
piece of the sample.

4)      
 



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