Recombinant DNA technology is the joining together of DNA molecules from two different species. The recombined DNA molecule is inserted into a host organism to produce new genetic combinations that are of value to science, medicine, agriculture, and industry. Since the focus of all genetics is the gene, the fundamental goal of laboratory geneticists is to isolate, characterize, and manipulate genes. Recombinant DNA technology is based primarily on two other technologies, cloning and DNA sequencing. Cloning is undertaken in order to obtain the clone of one particular gene or DNA sequence of interest. The next step after cloning is to find and isolate that clone among other members of the library (a large collection of clones). Once a segment of DNA has been cloned, its nucleotide sequence can be determined. Knowledge of the sequence of a DNA segment has many uses. The possibility for recombinant DNA technology emerged with the discovery of restriction enzymes in 1968 by Swiss microbiologist Werner Arber. The following year American microbiologist Hamilton O. Smith purified so-called type II restriction enzymes, which were found to be essential to genetic engineering for their ability to cleave at a specific site within the DNA (as opposed to type I restriction enzymes, which cleave DNA at random sites). Drawing on Smith’s work, American molecular biologist Daniel Nathans helped advance the technique of DNA recombination in 1970–71 and demonstrated that type II enzymes could be useful in genetic studies. About the same time, American biochemist Paul Berg developed methods for splitting DNA molecules at selected sites and attaching segments of the molecule to the DNA of a virus or plasmid, which could then enter bacterial or animal cells. In 1973 American biochemists Stanley N. Cohen and Herbert W. Boyer became the first to insert recombined genes into bacterial cells, which then reproduced. Read more below: Invention of recombinant DNA technology Read more about restriction enzymes. Through recombinant DNA techniques, bacteria have been created that are capable of synthesizing human insulin, human growth hormone, alpha interferon, hepatitis B vaccine, and other medically useful substances. Recombinant DNA technology also can be used for gene therapy, in which a normal gene is introduced into an individual’s genome in order to repair a mutation that causes a genetic disease. The ability to obtain specific DNA clones using recombinant DNA technology has also made it possible to add the DNA of one organism to the genome of another. The added gene is called a transgene, which can be passed to progeny as a new component of the genome. The resulting organism carrying the transgene is called a transgenic organism or a genetically modified organism (GMO). In this way a “designer organism” is made that contains some specific change required for an experiment in basic genetics or for improvement of some commercial strain. Read more below: DNA sequencing: Uses Learn more about gene therapy. recombinant DNA, molecules of DNA from two different species that are inserted into a host organism to produce new genetic combinations that are of value to science, medicine, agriculture, and industry. Since the focus of all genetics is the gene, the fundamental goal of laboratory geneticists is to isolate, characterize, and manipulate genes. Although it is relatively easy to isolate a sample of DNA from a collection of cells, finding a specific gene within this DNA sample can be compared to finding a needle in a haystack. Consider the fact that each human cell contains approximately 2 metres (6 feet) of DNA. Therefore, a small tissue sample will contain many kilometres of DNA. However, recombinant DNA technology has made it possible to isolate one gene or any other segment of DNA, enabling researchers to determine its nucleotide sequence, study its transcripts, mutate it in highly specific ways, and reinsert the modified sequence into a living organism. recombinant DNA In biology a clone is a group of individual cells or organisms descended from one progenitor. This means that the members of a clone are genetically identical, because cell replication produces identical daughter cells each time. The use of the word clone has been extended to recombinant DNA technology, which has provided scientists with the ability to produce many copies of a single fragment of DNA, such as a gene, creating identical copies that constitute a DNA clone. In practice the procedure is carried out by inserting a DNA fragment into a small DNA molecule and then allowing this molecule to replicate inside a simple living cell such as a bacterium. The small replicating molecule is called a DNA vector (carrier). The most commonly used vectors are plasmids (circular DNA molecules that originated from bacteria), viruses, and yeast cells. Plasmids are not a part of the main cellular genome, but they can carry genes that provide the host cell with useful properties, such as drug resistance, mating ability, and toxin production. They are small enough to be conveniently manipulated experimentally, and, furthermore, they will carry extra DNA that is spliced into them.
If you're seeing this message, it means we're having trouble loading external resources on our website. If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. DNA has many applications in a variety of fields including forensics and medicine. Key Points
The acronym “DNA” has become synonymous with solving crimes, testing for paternity, identifying human remains, and genetic testing. DNA can be retrieved from hair, blood, or saliva. Each person’s DNA sequences are unique, and it is possible to detect differences between individuals within a species on the basis of these unique features. DNA testing can also be used to identify pathogens, identify biological remains in archaeological digs, trace disease outbreaks, and study human migration patterns. In the medical field, DNA is used in diagnostics, new vaccine development, and cancer therapy. It is now also possible to determine predispositions to some diseases by looking at genes.
Reproductive cloning is a method used to make a clone or an identical copy of an entire multicellular organism. In cloning both the original organism and the clone have identical DNA. Identical twins are, in one sense, clones of each other; they have identical DNA, having developed from the same fertilized egg. Cloning became an issue in scientific ethics when a sheep became the first mammal cloned from an adult cell in 1996. Since then several animals such as horses, bulls, and goats have been successfully cloned, although these individuals often exhibit facial, limb, and cardiac abnormalities.  There have been attempts at producing cloned human embryos as sources of embryonic stem cells, sometimes referred to as ‘cloning for therapeutic purposes’. Therapeutic cloning produces stem cells to attempt to remedy detrimental diseases or defects (unlike reproductive cloning, which aims to reproduce an organism). Still, therapeutic cloning efforts have met with resistance because of bioethical considerations.
CRISPR (Clustered, Regularly-Interspaced Short Palindromic Repeats) allows scientists to edit genomes, far better than older techniques for gene splicing and editing. The CRISPR technique has enormous potential application, including altering the germline of humans, animals and other organisms, and modifying the genes of food crops. CRISPR Technique: This movie goes through the process of CRISPR.
A genetically modified organism (GMO) is any organism whose genetic material has been altered using genetic engineering techniques. GMOs are a source of medicines and genetically modified foods and are also widely used in scientific research, along with the production of other goods. Bacteria, plants, and animals have been genetically modified since the early 1970s for academic, medical, agricultural, and industrial purposes. In the US, GMOs such as Roundup-Ready soybeans and borer-resistant corn are part of many common processed foods. As in many of these biotechnology areas there is considerable controversy in the use of GMOs. |
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