Иностранные языки : HOW "DNA" TESTING WORKS (АНАЛИЗ "ДНК" КАК ПРОВЕРЯЮЩИЕ РАБОТЫ) - (реферат)

HOW "DNA" TESTING WORKS (АНАЛИЗ "ДНК" КАК ПРОВЕРЯЮЩИЕ РАБОТЫ) - (реферат)

Дата добавления: март 2006г.

    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:

Collectbiological 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. Isolatepure 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.

Amplifythe 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.

Segregatethe resulting DNA strands. A sample mixed with 13 primers multiplies into millions of distinctive molecules. Exposed to an electrical current, the molecules a sorted into color-coded bands on a gel.

Compare the crimescene samples with the suspect’s. Scientists say it’s virtually impossible for unrelated people to match up perfectly on