A woman using the microscope
- Everyone varies in this world; every insect, rabbit, dog, and human is unique.
- This uniqueness is established because every organism in this world has unique DNA (except identical twins).
- Hence DNA plays a significant role in shaping every life.
- In the current research scenario, DNA and genome have been studied thoroughly to understand and decode the mysteries of life. This has led to various methods to edit and manipulate DNA.
- The most recent method being developed is recombinant DNA technology (rDNA).
what is DNA technology
- It is a method by which a vector will express a piece of target DNA in a host organism.
- This technique requires a target DNA, a vector, a host organism, DNA modifying enzymes, restriction enzymes, and ligases.
- Using genetic engineering, the gene of interest is identified, isolated, and inserted into a plasmid or bacteriophage (vector) to form a recombinant DNA molecule.
Pictorial Representation of rDNA technology rDNA Technology
- 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.
Invention of DNA technology
- 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 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 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.
Goals of Recombinant DNA Technology
- To isolate and characterize a gene.
- To male the desired change in one or more isolated genes.
- To return changed/altered genes to living cells.
- Artificially synthesize new genes.
- Modifying the genome of an organism.
- Understanding hereditary diseases and their cure.
The rDNA technology protocol
- Identification of the gene of interest and then isolating that gene of interest or the DNA fragment to be cloned.
- Insert this isolated DNA fragment or gene of interest in a suitable vector.
- Transformation happens by introducing the vector into the host organism or cell.
- Then the transformed host cells are selected from the culture.
- Expression of the introduced gene or DNA fragment into the host is seen.
Diagram of a Microscope
DNA Modifying Enzymes
- Nuclease: They cut, degrade or shorten the nucleic acid molecules (they are what DNA is made of, kind of like leggo). Example: Lambda Exonuclease, Restriction endonuclease, etc.
- Ligases: They join nucleic acid molecules.
- Polymerases: They make copies of nucleic acid molecules. Example: DNA polymerase 1, Klenow fragment, Taq DNA fragment, Reverse Transcription, etc.
- Modifying Enzymes: They remove or add chemical groups in the nucleic acid molecules. Example: Alkaline phosphatase, T4 Polynucleotide Kinase, Terminal Deoxynucleotidyl Transferase, etc.
- The product of rDNA technology is Humulin used for diabetes, Humatrope for pituitary dwarfism, Intron A for hairy cell leukaemia, Recombinax HB for Hepatitis B etc.
This technology has been and is still being used for medical, pharmaceutical, and research purposes. There are several concerns for genetically developed products, but they also help treat conditions that general medicine could not have done in normal conditions.
Use of DNA technology
- 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.