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Polymerase Chain Reaction

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Introduction

Polymerase Chain Reaction "Investigate what PCR is - how has it revolutionised molecular biology and give several examples of how it is used?" PCR stands for polymerase chain reaction. This is a technique devised by Cary Mullis for cloning genes in a test tube without involving bacteria - and instead uses DNA polymerases (enzymes) to make multiple copies of a DNA strand. The polymerases must be able to function at high temperatures, so the enzymes are usually obtained from thermophilic bacteria such as Thermus aquaticus. To obtain the DNA, the sample of cells is placed into a solution, and solution is boiled, so the DNA is released. The DNA to be copied is placed in solution, and the temperature of this solution is then raised to 95?c to separate the two strands of DNA. ...read more.

Middle

sequentially to each strand, forming two new strings of DNA that complement the originals. Repetition of these steps doubles the amount of DNA present after each iteration. The proper experimental conditions induce these constituents to assemble two new copies from what was originally one DNA molecule. The steps involved take just a few minutes. And repeating the procedure doubles the number of copies each time. So 30 cycles of PCR produce a billion-fold increase of the targeted section of DNA, "amplifying" what might begin as a single molecule into enough material for easy examination. PCR enables DNA profiling to be used successfully on very small tissue samples, such as spots of blood, hair roots or a small semen stain. ...read more.

Conclusion

Robert Melias in 1987 was the first person to be convicted of a crime on the basis of evidence including DNA profiling. DNA profiling is now used in many thousands of criminal investigations each year. PCR can be used to help DNA profiling for these uses: detecting inherited diseases in embryonic cells, resolving paternity disputes, checking immigration applications, confirming animal pedigrees, and establishing genetic relationships between humans preserved in archaeological sites, such as peat bogs, etc, and people alive today. PCR is a very useful way of replicating DNA without the use of bacteria. It can be used for many different purposes, but its main use is in different crime cases, where only a very small amount of DNA has been left at the scene of the crime. It has been used very successfully thousands of times to correctly convict suspects of crimes they have committed. ?? ?? ?? ?? ...read more.

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