Lesson 5 Polymerase Chain Reaction-Xeroxing DNA Who would have thought a bacterium hanging out in a hot spring in Yelowstone National Park would spark a revolutionary new laboratory technique?The polymerase chain reaction,now widely used in research laboratories and doctor's officesrelies on the ability of DNA-copying enzymes to remain stable at high temperatures No problem for the sultry bacterium from Yellowstone tha now helps scientists produce millions of copies of a single DNA segment ina matter of hours. In nature,most organisms copy their DNA in the same way.The PCR mimics this process,only it does it ina test tube.When any cell divides,enzymes called polymerases make a copy of all the DNA in each chromosome.The first step in this process isto"two DNA chains of the double helix.As the two strands separate,DNA polymerase makes a copy using each strand as atemplate The four nucleotide bases,the building blocks of every piece of DNA,are represented by the letters A.C.Gand T,which stand for their chemical names:adenine.ytosine,guanine.and thymine.The Aon one strand always pairs with the Ton the other.whereas Calways pairs with G.The two strands are said to be complementary toeach other. To copy DNA.polymerase requires two other components a supply of the four nucleotide bases and something called a primer.DNA polymerases,whether from humans,bacteria,or viruses,cannot copya chain of DNA without a short sequence of nucleotides to"prime"the process or get it started Sothe cell has another enzyme called a primase that actually makes the first few nucleotides of the copy.This stretch of DNA is called a primer.Once the primer is made,the polymerase can take over making the rest of the new chain A PCR vial contains all the necessary components for DNA duplication:a piece of DNA,large quantities of the four nucleotides,large quantities of the primer sequence,and DNA polymerase.The polymerase is the Taq polymerase.named for which it was isolated. The three parts of the polymerase chain reaction are carried ou in the same vial.but at different temperatures.The first part of the process separates the two DNA chains in the double helix.This is done simply by heating the vial to-95 degrees centigrade (about 165 degrees Fahrenheit)for 30 sconds 99 Lesson 5 Polymerase Chain Reaction - Xeroxing DNA Who would have thought a bacterium hanging out in a hot spring in Yellowstone National Park would spark a revolutionary new laboratory technique? The polymerase chain reaction, now widely used in research laboratories and doctor's offices, relies on the ability of DNA-copying enzymes to remain stable at high temperatures. No problem for Thermus aquaticus, the sultry bacterium from Yellowstone that now helps scientists produce millions of copies of a single DNA segment in a matter of hours. In nature, most organisms copy their DNA in the same way. The PCR mimics this process, only it does it in a test tube. When any cell divides, enzymes called polymerases make a copy of all the DNA in each chromosome. The first step in this process is to "unzip" the two DNA chains of the double helix. As the two strands separate, DNA polymerase makes a copy using each strand as a template. The four nucleotide bases, the building blocks of every piece of DNA, are represented by the letters A, C, G, and T, which stand for their chemical names: adenine, cytosine, guanine, and thymine. The A on one strand always pairs with the T on the other, whereas C always pairs with G. The two strands are said to be complementary to each other. To copy DNA, polymerase requires two other components: a supply of the four nucleotide bases and something called a primer. DNA polymerases, whether from humans, bacteria, or viruses, cannot copy a chain of DNA without a short sequence of nucleotides to "prime" the process, or get it started. So the cell has another enzyme called a primase that actually makes the first few nucleotides of the copy. This stretch of DNA is called a primer. Once the primer is made, the polymerase can take over making the rest of the new chain. A PCR vial contains all the necessary components for DNA duplication: a piece of DNA, large quantities of the four nucleotides, large quantities of the primer sequence, and DNA polymerase. The polymerase is the Taq polymerase, named for Thermus aquaticus, from which it was isolated. The three parts of the polymerase chain reaction are carried out in the same vial, but at different temperatures. The first part of the process separates the two DNA chains in the double helix. This is done simply by heating the vial to 90-95 degrees centigrade (about 165 degrees Fahrenheit) for 30 seconds