Is It Possible To Take Dna From One Animal And Put It In Another Animal

GloFish are the get-go transgenic animals bachelor to the American public. But what's the biotechnology backside them?

Figure 1: The multicolored GloFish®.

Courtesy of www.glofish.com. All rights reserved.

"Seeing is believing with GloFish. They are admittedly stunning!" The preceding is some of the marketing material you'd read if you visited the GloFish website (GloFish, 2008). Beauty may exist in the center of the beholder, but nearly everyone would agree that these commencement—and, so far, only—transgenic animals made bachelor to the general public in the United states (except in California, pending a formal review of their potential effect on the environment) are a worthy conversation piece. A transgenic, or genetically modified, organism is one that has been contradistinct through recombinant DNA technology, which involves either the combining of Dna from different genomes or the insertion of foreign Deoxyribonucleic acid into a genome. GloFish (Figure one) are a type of transgenic zebrafish ( Danio rerio ) that have been modified through the insertion of a light-green fluorescent protein (gfp) gene. Non all GloFish are dark-green, however. Rather, there are several gfp gene constructs, each encoding a dissimilar colored phenotype, from fluorescent yellow to fluorescent crimson.

Currently, GloFish are the only recombinant-Dna animal that has been approved for human "apply" by the U.S. Food and Drug Administration. Their blessing has raised of import questions nigh whether, and to what extent, genetically modified animals should be fabricated available to consumers. But how were scientists able to create these engineered organisms in the starting time identify? Like and so many genetic technologies used today, recombinant Deoxyribonucleic acid technology had its origins in the late 1960s and early on 1970s. By the 1960s, scientists had already learned that cells repair DNA breaks past reuniting, or recombining, the broken pieces. Thus, it was only a affair of time before researchers identified the raw biological ingredients necessary for recombination, figured out how those ingredients functioned together, and and then tried to govern the recombining procedure themselves.

Early Experiments Provide the Footing for Recombinant Organisms

Although recombinant DNA engineering first emerged in the 1960s and 1970s, the basic principle of recombination had been discovered many years earlier. Indeed, in 1928, Frederick Griffith, an English language medical officer studying the bacteria responsible for a pneumonia epidemic in London, first demonstrated what he termed "genetic transformation"; here, living cells took up genetic material released by other cells and became phenotypically "transformed" by the new genetic information. More than a decade afterwards, Oswald Avery repeated Griffith's work and isolated the transforming molecule, which turned out to be Dna. These experiments showed that Dna can be transferred from one prison cell to some other in the laboratory, thus irresolute the bodily genetic phenotype of an organism.

Prior to these classic experiments, the thought that the genetic material was a specific chemical that could be modified and transferred into cells was certainly controversial. But before the explosion in recombinant Deoxyribonucleic acid could begin, scientists would take to learn not merely how to transfer Dna, but also how to isolate and change individual genes.

Key Developments in Recombinant Deoxyribonucleic acid Technology

Following these early experiments, four central developments helped lead to construction of the first recombinant DNA organism (Kiermer, 2007). The first 2 developments revolved around how scientists learned to cutting and paste pieces of DNA from dissimilar genomes using enzymes. The latter 2 events involved the development of techniques used to transfer foreign Dna into new host cells.

Discovering the Cutting-and-Paste Enzymes

The beginning major step forwards in the power to chemically change genes occurred when American biologist Martin Gellert and his colleagues from the National Institutes of Wellness purified and characterized an enzyme in Escherichia coli responsible for the actual joining, or recombining, of separate pieces of Dna (Zimmerman et al., 1967). They called their find "DNA-joining enzyme," and this enzyme is at present known equally Deoxyribonucleic acid ligase. All living cells utilize some version of Dna ligase to "mucilage together" brusque strands of Dna during replication. Using Eastward. coli extract, the researchers next showed that merely in the presence of ligase was it possible to repair unmarried-stranded breaks in λ phage Deoxyribonucleic acid. (Discovered in 1950 past American microbiologist Esther Lederberg, λ phage is a virus particle that infects East. coli.) More specifically, they showed that the enzyme was able to form a 3'-5'-phosphodiester bond between the 5'-phosphate end of the terminal nucleotide on ane Deoxyribonucleic acid fragment and the 3'-OH finish of the concluding nucleotide on an adjacent fragment. The identification of Deoxyribonucleic acid ligase was the first of several fundamental steps that would eventually empower scientists to attempt their ain recombination experiments—experiments that involved not but recombining the DNA of a single individual, merely recombining DNA from unlike individuals, including unlike species.

A second major step frontwards in factor modification was the discovery of restriction enzymes, which cleave DNA at specific sequences. These enzymes were discovered at approximately the same fourth dimension as the showtime DNA ligases by Swiss biologist Werner Arber and his colleagues while they were investigating a phenomenon called host-controlled restriction of bacteriophages. Bacteriophages are viruses that invade and oftentimes destroy their bacterial host cells; host-controlled brake refers to the defense mechanisms that bacterial cells have evolved to bargain with these invading viruses. Arber's team discovered that 1 such mechanism is enzymatic activity provided by the host jail cell. The team named the responsible enzymes "brake enzymes" because of the way they restrict the growth of bacteriophages. These scientists were as well the get-go to demonstrate that restriction enzymes impairment invading bacteriophages by cleaving the phage Dna at very specific nucleotide sequences (now known as brake sites). The identification and characterization of brake enzymes gave biologists the ways to cutting specific pieces of DNA required (or desired) for subsequent recombination.

Inserting Foreign DNA into a New Host Jail cell

Although Griffith and Avery had had demonstrated the ability to transfer foreign genetic fabric into cells decades before, this "transformation" was very inefficient, and it involved "natural" rather than manipulated Dna. Only in the 1970s did scientists brainstorm to employ vectors to efficiently transfer genes into bacterial cells. The first such vectors were plasmids, or pocket-sized DNA molecules that live naturally inside bacterial cells and replicate separately from a bacterium'due south chromosomal Dna.

Plasmids' utility as a Deoxyribonucleic acid shuttle, or vector, was discovered by Stanford University biochemist Stanley Cohen. Scientists had already established that some bacteria had what were known as antibiotic resistance factors, or R factor-plasmids that replicated independently within the bacterial cell. But scientists knew little about how the different R factor genes functioned. Cohen thought that if there were an experimental arrangement for transforming host bacterial cells with these R-gene DNA molecules, he and other researchers might be able to ameliorate understand R-factor biological science and effigy out exactly what it was about these plasmids that fabricated leaner antibiotic-resistant. He and his colleagues developed that organisation past demonstrating that calcium chloride-treated Due east. coli tin be genetically transformed into antibiotic-resistant cells by the add-on of purified plasmid DNA (in this case, purified R-factor DNA) to the bacteria during transformation (Cohen et al., 1972).

Recombinant Plasmids in Leaner

The following year, Stanley Cohen and his colleagues were too the first to construct a novel plasmid Dna from two divide plasmid species which, when introduced into Eastward. coli, possessed all the nucleotide base sequences and functions of both parent plasmids. Cohen's team used brake endonuclease enzymes to cleave the double-stranded Dna molecules of the two parent plasmids. The team next used Dna ligase to rejoin, or recombine, the Deoxyribonucleic acid fragments from the 2 different plasmids (Figure two). Finally, they introduced the newly recombined plasmid DNA into E. coli. The researchers were able to bring together two Deoxyribonucleic acid fragments from completely dissimilar plasmids because, equally they explained, "the nucleotide sequences cleaved are unique and cocky-complementary so that Deoxyribonucleic acid fragments produced by one of these enzymes can associate by hydrogen-bonding with other fragments produced by the aforementioned enzyme" (Cohen et al., 1973).

The same could exist said of any Deoxyribonucleic acid—not just plasmids—from two unlike species. This universality—the chapters to mix and lucifer Dna from different species, considering DNA has the same structure and function in all species and because brake and ligase enzymes cut and paste the same ways in unlike genomes—makes recombinant Deoxyribonucleic acid biology possible.

Today, the E. coli λ bacteriophage is 1 of the most widely used vectors used to carry recombinant DNA into bacterial cells. This virus makes an excellent vector because about one-third of its genome is considered nonessential, pregnant that it can be removed and replaced by foreign DNA (i.e., the Deoxyribonucleic acid beingness inserted). As illustrated in Figure 3, the nonessential genes are removed by restriction enzymes (the specific restriction enzyme EcoRI is shown in the figure), the foreign DNA inserted in their place, and and then the final recombinant DNA molecule is packaged into the virus'due south protein glaze and prepped for introduction into its host jail cell.

Vectors Used in Mammalian Cells

A fourth major step forward in the field of recombinant Dna technology was the discovery of a vector for efficiently introducing genes into mammalian cells. Specifically, researchers learned that recombinant Deoxyribonucleic acid could be introduced into the SV40 virus, a pathogen that infects both monkeys and humans. Indeed, in 1972, Stanford University researcher Paul Berg and his colleagues integrated segments of λ phage DNA, as well as a segment of E. coli DNA containing the galactose operon, into the SV40 genome. (The East. coli galactose operon is a cluster of genes that plays a role in galactose sugar metabolism.) The significance of their accomplishment was its sit-in that recombinant DNA technologies could be applied to substantially any Deoxyribonucleic acid sequences, no matter how distantly related their species of origin. In their words, these researchers "developed biochemical techniques that are generally applicable for joining covalently any two Dna molecules" (Jackson et al., 1972). While the scientists didn't actually introduce strange Dna into a mammalian prison cell in this experiment, they provided (proved) the means to do so.

Recombinant Dna Technology Creates Recombinant Animals

The first bodily recombinant animal cells weren't developed until nigh a decade afterward the research conducted by Berg's team, and well-nigh of the early studies involved mouse cells. In 1981, for example, Franklin Costantini and Elizabeth Lacy of the Academy of Oxford introduced rabbit Dna fragments containing the developed beta globin gene into murine (mouse) germ-line cells (Costantini & Lacy, 1981). (The beta globins are a family of polypeptides that serve every bit the subunits of hemoglobin molecules.) Some other grouping of scientists had demonstrated that foreign genes could be successfully integrated into murine somatic cells, only this was the first demonstration of their integration into germ cells. In other words, Costantini and Lacy were the first to engineer an entire recombinant animal (albeit with relatively low efficiency).

Interestingly, not long after the publication of his squad's 1972 study, Paul Berg led a voluntary moratorium in the scientific community against sure types of recombinant DNA research. Clearly, scientists have always been aware that the ability to manipulate the genome and mix and lucifer genes from different organisms, fifty-fifty unlike species, raises immediate and serious questions about the potential hazards and risks of doing so—implications still existence debated today.

Since these early studies, scientists have used recombinant DNA technologies to create many unlike types of recombinant animals, both for scientific report and for the profitable manufacturing of human proteins. For case, mice, goats, and cows have all been engineered to create medically valuable proteins in their milk; moreover, hormones that were once isolated merely in minor amounts from human cadavers can at present be mass-produced by genetically engineered cells. In fact, the entire biotechnology industry is based upon the ability to add together new genes to cells, plants, and animals As scientists discover important new proteins and genes, these technologies will continue to form the foundation of future generations of discoveries and medical advances.

References and Recommended Reading

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Cohen, S. N., et al. Nonchromosomal antibiotic resistance in bacteria: Genetic transformation of Escherichia coli by R-factor Dna. Proceedings of the National Academy of Sciences 69, 2110–2114 (1972)

———. Construction of biologically functional bacterial plasmids in vitro. Proceedings of the National Academy of Sciences 70, 3240–3244 (1973)

Costantini, F., & Lacy, Eastward. Introduction of a rabbit beta-globin gene into the mouse germ line. Nature 294, 92–94 (1981) (link to article)

Crea, R., et al. Chemical synthesis of genes for human insulin. Proceedings of the National Academy of Sciences 75, 5765–5769 (1978)

GloFish. GloFish dwelling house page. www.glofish.com (Accessed July 3, 2008)

Jackson, D. A., et al. Biochemical method for inserting new genetic information into DNA of simian virus 40: Circular SV40 DNA molecules containing lambda phage genes and the galactose operon of Escherichia coli. Proceedings of the National Academy of Sciences 69, 2904–2909 (1972)

Kiermer, V. The dawn of recombinant Dna. Nature Milestones: Dna Technologies, http://www.nature.com/milestones/miledna/full/miledna02.html (2007) (link to article)

Miller, H. I. FDA on transgenic animals—A domestic dog's breakfast? Nature Biotechnology 26, 159–160 (2008) (link to article)

Zimmerman, Due south. B., et al. Enzymatic joining of DNA strands: A novel reaction of diphosphopyridine nucleotide. Proceedings of the National Academy of Sciences 57, 1841–1848 (1967)

Source: http://www.nature.com/scitable/topicpage/recombinant-dna-technology-and-transgenic-animals-34513

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