التفاعل المتسلسل للبوليميرات ( Polymerase Chain Reaction )


(nwr4u) #1

[CENTER]التفاعل المتسلسل للبوليميرات

( Polymerase Chain Reaction )[/center]

The Polymerase chain reaction is a method for making many copies of a specific segment of DNA , starting with a very small amount .[COLOR=red][FONT=Simplified Arabic]

This technique can be used to identify specific microorganisms from a small amount of DNA and to identify persons involved in crimes from DNA on Cigarettes in a single hair follicle .

The DNA to be amplified is mixed with deoxyribonucleotides , a thermal stable DNA polymerase called Taq Polymerase and DNA primers .

[B]The mixture is heated to break the hydrogen bonds in the DNA , forming single- started molecules . The mixture is then cooled sufficiently to allow the DNA primers to anneal to each end of the segment to be copied .[COLOR=black][FONT=Simplified Arabic]

Taq Polymerase then synthesizes the complementary strand of DNA , using yhe primer as the starting point .[/font][/color][/b]

[B]The temperature is raised again to separate the DNA stands and then lowered sufficiently to allow the primers to attach . Taq Polymerase now synthesizes another set of new complementary strands . [COLOR=black][FONT=Simplified Arabic]

[I][B]This process is repeated until enough DNA has been produced to be identified or used for further research . After twenty-one cycles , one molecules of DNA can be amplified to over a million copies .[COLOR=black][FONT=Simplified Arabic]

This amount of amplification can be achieved by running the reaction overnite in a thermal cycle , an instrument that automatically raises and lowers the temperature at appropriate time intervals .

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(system) #2

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(nwr4u) #3

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