Polymerase Chain Reaction

The advantages of PCR

The raw materials

The Stages

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The Polymerase Chain Reaction

- PCR allows gene cloning to take place in a test tube

- Reaction allows many identical copies of double stranded DNA to be made without the use of bacteria

- Each strand is copied producing two new strands, doubling the amount each cycle

- This is semi-consevative replication of DNA

- PCR is used to create vast quantities of DNA from small samples such as a speck of blood

- It gives enough material for genetic fingerprinting.

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The raw materials for PCR

- Taq DNA Polymerase is heat stable

- four different types of nucleotides containing bases, adenine, guanine, cytosine and thymine

- Short lengths of 20-30 nucleotides single strand pieces of DNA called primers -these act as signals to Taq polymerase enzyme to start copying

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Stages in PCR

Strand Separation - The original DNA is heated to 95 C to break hydrogen bonds between bases, separating into 2 strands of DNA

Primer Binding: The solution is cooled rapidly cooled to 55 C for primers to bind to complementary base sequences on each of the single strands of DNA, providing a starting point for DNA replication

STrand Synthesis: solution is heated to 70 C and the Taq polymerase catalyses the synthesis of a complementary strand for each of the single strands of DNA using a supply of nucleotides, producing two identical strands of DNA

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