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Since Ian Wilmut and colleagues at the Roslin Institute in Edinburgh cloned a sheep called Dolly in 1996 [1], researchers have reported cloning dozens of mice and several cows. Most recently, scientists in Korea report the cloning of human embryos and their subsequent survival in vitro to the eight-cell stage [2]. Meanwhile, the physicist Richard Seed has proposed cloning himself. These accomplishments and their potential applications have excited a vigorous debate in the public and the popular press on the ethics of cloning (see newspapers, magazines, books, television programs, and shopper's tabloids).
At this time we feel compelled to draw attention to an issue that has heretofore been missing from the public debate. For years, it has been common practice among biologists to clone things. Cloning of genes and large fragments of DNA is so commonplace that standard cloning manuals are veritable laboratory bibles [3,4]. The procedures described in these references are so simple that even graduate students can perform them with ease.
An important yet unacknowledged observation, however, is that biologists often fail to perform even simple cloning very well. Although many of the techniques used in molecular biology are straightforward, they are by no means foolproof. In fact, certain mishaps are so commonplace that in many laboratories an extensive nomenclature has arisen to describe them.
Here, to inform public debate on questions about technical and ethical aspects of cloning, we delineate a few of the more common experimental errors. To our knowledge, these procedures have not yet been formally incorporated into the popular laboratory manuals used by biologists who regularly attempt cloning. Nonetheless, we believe that they will be instantly recognizable to anyone who has inadvertently performed them.
Sink filtration. By far one of the most basic and frequently performed procedures for eliminating experimental results, sink filtration involves pouring the critical samples down the drain.
Efficient performance of this technique is enhanced by the presence of distractions in the laboratory environment. Hood fires, Eppendorf fights, and loud music (especially the Goo Goo Dolls and Screeching Weasel) are particularly effective.
Waste transformation. An even more elegant method for one-step sample disposal entails simply depositing the item of interest directly into the trash. Recovery generally depends on receptacle size (see figure 2). The other critical factor is how quickly the investigator realizes that the procedure has been performed (see figure 3). Reverse fractionation. Somewhat more time-consuming than sink filtration or waste transformation, this procedure usually involves a fraction collector jamming during an overnight protein purification, allowing column samples to run out onto the cold room floor. Pooled samples can be recovered by the rather laborious linoleum elution method, although more commonly they are transferred directly to paper towels and discarded. Beverage dialysis. This fairly haphazard method for rapidly disposing of nonpermitted potables is performed in conjunction with the unexpected appearance of the institution's radiation safety inspector. Although the procedure works best for colorless liquids that are undetectable when rapidly mixed with large volumes of dialysis buffer, it has also been performed with varying degrees of success using coffee, Diet Coke, Mountain Dew, Guinness Stout, and V8 vegetable juice. An unsuccessful beverage dialysis is almost always followed by isotope-flow disruption. Gel fractionation. Most molecular biology laboratories rely heavily on gel electrophoresis methods to separate DNA samples. Several additional methods allow DNA samples to be separated efficiently from the investigator Mishandling of the sample at this point frequently leads to gel fractionation. Further, if the gel is not recovered promptly, the experimenter may wind up performing an unintended footprint analysis. Projectile PCR. This unique method of sample ejection was developed in the laboratory of Ken Kinzler and Bert Vogelstein at the Johns Hopkins
University School of Medicine in Baltimore. Today, few molecular biology laboratories are without a modern thermal cycler for performing the polymerase chain reaction (PCR) used to amplify DNA samples.
Large-scale methods. Simple, large-scale methods also exist for the random or total loss of experimental samples. In conclusion, given the evident aptitude of molecular biologists for continually devising newer and more innovative methods of mucking up even the most routine experiments, we strongly recommend that pioneering investigators such as Richard Seed think twice about their cloning plans. Acknowledgments The authors wish to thank Ken Chang of ABCNEWS.com for scanning the images, and the members of the Kinzler/Vogelstein lab for demonstrating the successful application of these disastrous techniques. This article is adapted from a presentation given in 1998 at the Franklin Institute in Philadelphia as part of an event sponsored by the Annals of Improbable Research. Endlinks Clones-R-Us
- Order a so-called designer clone featuring the DNA of such people as Cindy Crawford or "early Michael Jackson." Explored in depth in a previous HMS Beagle Site Review.
Conceiving a Clone
- a Web site that bills itself as "the largest cloning site on the
Web" and includes technical, historical, legal, and philosophical
background, a summary of the ongoing debates on cloning, and a reader poll
on whether human cloning should be allowed.
Roslin Institute
- Information on cloning and nuclear transfer.
Sink filtration is so simple that even a skilled principal investigator can perform it effortlessly. Even after careful extraction, sample recovery is generally poor
(see figure 1).
Figure 1
Figure 2
Figure 3
Linoleum blotting. This technique involves placing a gel firmly in contact with floor tiles (see figure 4).
Figure 4
In a related procedure, the experimenter may leave a gel momentarily on a nearby lab stool. The resulting analysis is known as a butt blot (see figure 5).
Figure 5
Before PCR became fully automated, however, cyclers tended to fling samples across the laboratory - at least in the hands of Kinzler and Vogelstein. The resulting procedure quickly became known as projectile PCR. Generally speaking, sample recovery was poor. With the proper equipment in the hands of a skilled student or postdoc, however, recovery improved dramatically (see figure 6).
Figure 6
Karen Hopkin is a freelance writer in Silver Spring, Maryland. She holds a Ph.D in biochemistry and has seen many of the above procedures performed firsthand.
William Gerson is a name derived from an anagram of the name of a West Coast researcher who would prefer his contribution to this piece to remain anonymous.
Andrzej Krauze is an illustrator, poster maker,
cartoonist, and painter who illustrates regularly for
HMS Beagle, The Guardian, The Sunday Telegraph,
Bookseller, and New Statesman.
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