Download Title: Ready, Set, Clone! Authors: Kowalski, Kathiann M. Source

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