The first transgenic animals made available are America are glofish

“Seeing is believing with GloFish. In every sense, these are breathtaking!” If you visited the GloFish website, you would see some advertising above (GloFish, 2008). They are the first—and, to date, the only—transgenic animals made available to the general population in the United States. While the idea of beauty may differ from person to person, almost everyone would agree that it is essential (with the exception of California, pending a formal review of its potential environmental impact). An organism that has undergone genetic modification utilizing recombinant DNA technology is called a transgenic organism. This process may involve fusing DNA from different genomes or introducing foreign DNA into a genome.

The transgenic zebrafish (Danio rerio) subspecies known as “GloFish” have the green fluorescent protein (GFP) gene added. Yet, not every GloFish is green. Instead, a variety of GFP gene constructs are known, each of which codes for a different colored phenotype, from brilliant red to luminous yellow. The GloFish is the first recombinant-DNA animal that has currently been given US Food and Drug Administration approval for “use” in humans. Their acceptance has drawn attention to crucial questions regarding whether and how many genetically modified animals should be made available to people. But how did scientists initially manage to produce these synthetic organisms? Recombinant DNA technology was developed in the late 1960s and early 1970s, like many other genetic technologies in use today. Scientists discovered in the 1960s that cells mend DNA breaks by reassembling, or recombining, the damaged components. So, it was only a matter of time until scientists discovered the basic biological components required for recombination, understood how those components worked together and then attempted to control the recombining process on their own.

Recombinant organisms are built on early experiments.

While recombinant DNA technology initially appeared in the 1960s and 1970s, the fundamentals of recombination were known for a long time before that. Indeed, Frederick Griffith, an English medical officer researching the pneumonia-causing bacteria in London, first demonstrated what he called “genetic transformation” in 1928. In this case, living cells absorbed genetic material released by other cells and underwent phenotypic “transformation” due to the new genetic information. Oswald Avery continued Griffith’s research more than ten years later and discovered the changing molecule, which turned out to be DNA. These studies demonstrated that DNA may be transferred between lab-grown cells, altering the genetic phenotype of an organism. The notion that the genetic material was a particular substance that could be altered and transferred into cells was clearly debatable prior to this groundbreaking research. But, before the explosion in recombinant DNA could start, researchers would need to master the techniques for isolating and modifying specific genes in addition to DNA transfer.

Significant Advances in Recombinant DNA Technologies

Four significant advancements after these initial efforts helped create the first recombinant DNA organism (Kiermer, 2007). The first two advancements focused on how scientists discovered how to use enzymes to clip and paste DNA fragments from various genomes. The last two occasions entailed the invention of methods for introducing foreign DNA into fresh host cells.

More specifically, they demonstrated that the enzyme was capable of forming a 3′-5′-phosphodiester link between the 3′-OH end of one DNA fragment’s last nucleotide and the 5′-phosphate end of another fragment’s last nucleotide. The discovery of DNA ligase was the first of several crucial milestones that would eventually enable scientists to conduct their own recombination studies, including those that required merging DNA from various persons, including various species, rather than just that of a single individual.

The discovery of restriction enzymes, which cut DNA at particular sequences, was a second significant advancement in gene editing. While researching a phenomenon known as host-controlled restriction of bacteriophages, Swiss biologist Werner Arber and his colleagues discovered these enzymes around the same time as the first DNA ligases. Host-controlled restriction refers to the defense mechanisms that bacterial cells have developed to deal with these invading viruses. Bacteriophages are viruses that infect and frequently kill their bacterial host cells. One such method was identified by Arber’s team as being given by the host cell’s enzymatic activity. Because the relevant enzymes limit the development of bacteriophages, the scientists gave them the term “restriction enzymes.” Also, these researchers were the first to show that restriction enzymes harm bacteriophages that invade host cells by cleaving phage DNA at highly particular nucleotide sequences (now known as restriction sites). The discovery and characterization of restriction enzymes provided scientists with the tools to remove specific DNA fragments needed (or wanted) for recombination to take place.

Foreign DNA Injection into a New Host Cell

Although Griffith and Avery had decades previously shown that it was possible to introduce foreign genetic information into cells, this “transformation” was incredibly ineffective and used “natural” DNA as opposed to DNA that had been artificially altered. Scientists didn’t start effectively transferring genes into bacterial cells with vectors until the 1970s. Plasmids, which are tiny DNA molecules that naturally reside inside bacterial cells and multiply independently of a bacterium’s chromosomal DNA, was the first of these vectors. Stanley Cohen, a scientist at Stanford University, first realized the potential of plasmids as a DNA shuttle or vector. The existence of R factor-plasmids, or bacteria with plasmids that replicated autonomously inside the bacterial cell, was already known to scientists to exist in some bacteria. But nothing was known about how the various R factor genes worked. Cohen reasoned that if there were a system for experimentally introducing these R-factor DNA molecules into host bacterial cells, he and other researchers might be able to comprehend R-factor biology and determine precisely what it was about these plasmids that made bacteria resistant to antibiotics. He and his colleagues created that system by demonstrating that the addition of purified plasmid DNA (in this case, purified R-factor DNA) to calcium chloride-treated E. coli during transformation can genetically change the bacteria into antibiotic-resistant cells (Cohen et al., 1972).

Bacterial Recombinant Plasmids

The next year, Stanley Cohen and his coworkers created the first unique plasmid DNA from two distinct plasmid species that, when inserted into E. coli, contained all of the nucleotide base sequences and functionalities of both parent plasmids. In order to cleave the double-stranded DNA molecules of the two parent plasmids, Cohen’s team utilized restriction endonuclease enzymes. The scientists then rejoined, or recombined, the DNA fragments from the two distinct plasmids using DNA ligase. The newly merged plasmid DNA was then inserted into E. coli. According to their statement, “the nucleotide sequences cleaved are distinct and self-complementary so that DNA fragments produced by one of these enzymes can associate with other pieces produced by the same enzyme by hydrogen bonding.” This enabled the researchers to combine two DNA snippets from two distinct plasmids (Cohen et al., 1973). Not just plasmids, but any DNA from two different species might be said to possess this feature. Recombinant DNA biology is plausible due to the universality of DNA, or the capacity to combine DNA from different species, which is made possible by the fact that DNA has the same structure and function in all species and that restriction and ligase enzymes cut and paste DNA in various genomes in the same way. One of the most often utilized vectors for introducing recombinant DNA into bacterial cells nowadays is the E. coli bacteriophage. Because around one-third of this virus’s genome is deemed non-essential, meaning that it can be deleted and replaced with foreign DNA, it makes a great vector (i.e., the DNA being inserted).