Polymerase chain reaction (PCR) allows researchers to amplify DNA in a test tube. This process uses an enzyme derived from heat-resistant bacteria. The steps of PCR are driven by changes in temperature.
Until the mid-1980s, the only way to make many copies of DNA was to insert the DNA pieces into bacteria and select the desired one from many different colonies growing on a plate. In 1985, Kary Mullis invented a precise and radical new method of selecting and amplifying a section of DNA ? the polymerase chain reaction (PCR).
(DNAi Location: Manipulation > Techniques > Amplifying > PCR animation)
Duration: 1 minutes 27 seconds
Polymerase chain reaction, or PCR, uses repeated cycles of heating and cooling to make many copies of a specific region of DNA. First, the temperature is raised to near boiling, causing the double-stranded DNA to separate, or denature, into single strands. When the temperature is decreased, short DNA sequences known as primers bind, or anneal, to complementary matches on the target DNA sequence. The primers bracket the target sequence to be copied. At a slightly higher temperature, the enzyme Taq polymerase, shown here in blue, binds to the primed sequences and adds nucleotides to extend the second strand. This completes the first cycle. In subsequent cycles, the process of denaturing, annealing and extending are repeated to make additional DNA copies. After three cycles, the target sequence defined by the primers begins to accumulate. After 30 cycles, as many as a billion copies of the target sequence are produced from a single starting molecule.
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DNA polymerase (blue) makes many copies of DNA (red) in a cycle of the polymerase chain reaction (PCR).
Polymerase chain reaction (PCR) enables researchers to produce millions of copies of a specific DNA sequence in approximately two hours. This automated process bypasses the need to use bacteria for amplifying DNA.
The DNA sequencing method developed by Fred Sanger forms the basis of automated "cycle" sequencing reactions today.
Kary Mullis explains how the polymerase chain reaction (PCR) was named.
Kary Mullis talks about his discovery of the polymerase chain reaction (PCR), a process that allows chemists to produce many copies of a specific fragment of DNA.
Image of Kary Mullis. In 1985, Kary Mullis invented the polymerase chain reaction (PCR), a method of amplifying or producing many copies of a specific piece of DNA. The revelation came to this eccentric character on a drive in northern California.
Kary Mullis speaks about the process of find a specific fragment of DNA amongst many pieces in a complex mixture.
Fred Sanger outlines DNA sequencing.
KARY MULLIS (1944- )
Transcription factors bind to DNA, RNA polymerase begins transcribing messanger RNA (mRNA) molecule from DNA.