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Download Title: Ready, Set, Clone! Authors: Kowalski, Kathiann M. Source
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Title: Authors: Source: Document Type: Subject Terms: Abstract: Lexile: Full Text Word Count: ISSN: Accession Number: Ready, Set, Clone! Kowalski, Kathiann M. Odyssey, Mar2011, Vol. 20 Issue 3, p32-34, 3p Article DNA MOLECULAR cloning The article presents information on DNA cloning or DNA copying. 1120 835 01630946 58745011 Persistent http://search.ebscohost.com/login.aspx?direct=true&db=mih&AN=58745011&site= link to this ehost-live record (Permalin k): Cut and Paste: <a href="http://search.ebscohost.com/login.aspx?direct=true&db=mih&AN=58745011 &site=ehost-live">Ready, Set, Clone!</a> Database: Middle Search Plus What do scientists do when their research calls for copying DNA? Standard office copiers can't reproduce the long, twisted-helix molecules that encode genetic information Fortunately, scientists have other ways to get the job done. When technicians find DNA at a crime scene, there may not be enough to identify a criminal. But if scientists can amplify, or increase, the amount of DNA by making many copies, they can help solve the crime. Sometimes scientists want to study a specific gene. To get enough to work with, they need to clone, or copy, the DNA that makes up that gene. "Cloning allows us to study how individual genes function in controlling the cell's activities." notes biologist Stephen Free at the University at Buffalo. Scientists also copy DNA when they study different proteins. Basically, genes tell cells to make particular proteins. So if scientists want bacteria ox yeast to produce a protein they don't normally make, they need copies of the right gene, and then they need to get the copies into those cells. "We can turn these little bacteria into factories that generate a whole lot of whatever protein it is that we're interested in," says biologist Clare O'Connor at Boston College. Probably the biggest DNA cloning job so far was the Human Genome Project, which figured out the order of the 3 billion base pairs in human DNA. That 13-year job involved making many copies of DNA pieces that were up to 1,000 or so base pairs long. Then scientists figured out how the pieces fit together. "It was like putting together a puzzle," explains O'Connor. Copying in Action A business office copier is usually a hefty machine that uses ink and paper. In the biology lab, says O'Connor, "the copier that we're using is DNA polymerase." DNA polymerase acts as a catalyst to make DNA copy itself. When DNA replicates, it first unwinds into separate strands. Then individual nucleotides in the DNA pair up with their partners. Adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G). The result is two identical copies of the original DNA strand. When DNA replication occurs inside a cell, the cell already contains DNA polymerase. Thus, if scientists can get copied genes into certain kinds of bacteria or yeast, those cells will automatically copy the genes each time they reproduce. In other cases, scientists copy bits of DNA with a PCR machine. PCR stands for polymerase chain reaction. Scientists put some original DNA and polymerase in a tiny test tube called an Eppendorf tube. They add proteins called "restriction enzymes" to cut out the specific DNA section they want. They also add "primers/' which contain the A, C, G, and T nucleotides. The unwound DNA strands will need the primers to make the other half of the DNA molecule's helix or ladder. To help the reaction along, the machine goes through three different heat cycles, over and over. When all the cycles finish, the gene will have copied itself many, many times. Cloning Comes in Handy Laboratory copying methods let scientists do basic research. For example, Free studies how genes and proteins affect how cell walls form in fungi. O'Connor examines how a particular protein may help cells fight off age damage. Cloning already helps make vaccines. Cloning also helps make medicines for diabetes, heart disease, and other ailments. More fundamentally, cloned genes let scientists understand how malfunctions in genes and proteins produce diseases, such as muscular dystrophy. When scientists can see how the genes act in model organisms, such as mice, they may be able to figure out possible treatments. Cloning also affects products we use every day. Enzymes in laundry detergent come from cloning. And factories make high fructose corn syrup for sodas, cookies, and other foods with proteins from cloned genes. Cloned genes might have sounded farfetched a century ago. Now, says Free, "They're very much part of our life." (Try "The Secret of Life" Activity, p. 36, to see how DNA makes perfect copies of itself naturally.) Kathiann M. Kowalski learned how to use a PCR machine when she did a science writers' fellowship at the Marine Biological Laboratory in Woods Hole, Massachusetts. She lives in Ohio and writes often for ODYSSEY. Catalyst -- A substance that triggers or speeds up a chemical reaction without taking part in the reaction itself DNA (deoxyribonucleic acid) -- A long molecule shaped like a twisted ladder, with base pairs that encode genetic information A molecular model of Taq polymerase replicating DNA. Taq polymerase is widely used in the polymerase chain reaction (PCR), a biochemical technique to mass-produce a portion of DNA. The Taq polymerase is blue and the two strands of DNA are green. A researcher prepares DNA for replication during the 13-year-long Human Genome Project, which figured out the order of the 13 billion base pairs in human DNA. A PCR machine being used in a virology department ~~~~~~~~ By Kathiann M. Kowalski