Genetic Engineering


Genetic engineering is the process of adding, replacing or removing genetic units for the better, permanent and heritable changes in different plants and animals. It is also known as the technique which deals with the recombinant of DNA. In this technique DNA of species in inserted into the DNA of vector such as plasmid, cosmid, virus, etc. In this technology terms such as “gene surgery”, “gene manipulation”, “gene therapy”, “gene transplantation”, etc. commonly used.

Source: fig: Cloning Strategy
fig: Cloning Strategy

Genetic engineering deals with the detailed knowledge of gene, its molecular structure and nature as well the ability to manipulate cells of higher plants or animals to the different vector DNA. Present world is amazed with the research of this technology. It is has been a great revolution to the world of biology. This technique has brought different useful and better species of the plants and animals. Scientists have done many researches such as they have introduce the Luciferase gene from firefly to the tobacco plant to measure the light emitted by the plants and other they have introduce the nitrogen fixation gene (NIF gene) and bacillus thuringinensis (Bt)gene in the cereals plants has help agriculture a lot. This technique is able to identify different genetic diseases in human being as well as its cure.

Genetic engineering has brought a great revolution in the sector of agriculture. This technique has brought different improvement in the plants which are able to good in both quality and quantity. This technique is able to produce different plants which are diseases resistant, has all the required nutrients, resistance to fungal, bacteria and virus. This technique has done great work in the field of medical science too.

Cloning of DNA (Technique of Recombinant DNA technology)

Cloning of DNA technique involves with three steps. In first step, the DNA of the organism having desirable gene is cut into the very small pieces. This gene is known as target gene or foreign gene.

In second step, the targeted DNA is joined (in vitro) artificially to a second piece of DNA which can replicate itself and attach itself to the other target DNA. The secondly formed DNA is known as vector or cloning vehicle. The joined hybrid molecule, recombinant DNA, consist of two type of DNA arranged in one another in circular structured DNA.

In third step, the DNA formed by the combination of vector and target is introduce into the living cell. That cell work as biological copying machine which produce the many copies of the hybrid DNA. This process is known as molecular cloning.

Tools of gene cloning

Cloning is the basic step of recombinant DNA technology in which foreign DNA is attached to vector. Cloning of DNA has different tools which are mentioned below:

  1. Restriction endonucleases or enzymes- Double stranded DNA is cleave into smaller fragments by these enzymes. These enzymes are also known as the molecular scissors which cut DNA at specific sites when come in contact. Restriction enzymes are taken out from the bacteria and also name after the name of bacteria from which they are taken out. There are about hundred different restriction enzymes derived from different bacteria. Ecor1 is one of the best known restriction enzyme. Some of the examples of restriction enzymes are; Hind III, Bam H1, Sau3 A1, etc.
  2. DNA ligase- The 3’ – hydroxyl end of one strand of DNA is covalently link to the 5’- phosphate ends of the second strand DNA by DNA ligase. DNA ligase is able to join the DNA segments that are cut by the restriction enzymes.
  3. Vector- It is defined as the DNA in which target DNA is inserted for cloning. To be a vector they must have following characters:
  • Vector should be able to replicate inside the host cell.
  • They must have capacity to insert inside the host cell.
  • They must be able to select the marker.

Major types of vectors

  1. Plasmids- They are the circular piece of DNA present in bacteria which has extra chromosome. They are also known as keys cloning vectors. They have different features which are as follows:
  • They are able to replicate within the host bacterium and have their own origin of replication.
  • They have the gene of protein which help to form antibiotics resistant host, since antibiotics resistant gene is used in the formation of them.

Types of plasmids

  • Ti plasmid-These plasmids are natural plasmids, found in the tumor cells which are produced by Agrobacterium tumefaciens.
  • Plasmids pBR322- These plasmids are the best known bacterial plasmid use for cloning.
  1. Cosmids- They are defined as the plasmids containing a fragment of DNA consisting cos site. Large DNA fragment cloning can be done with the help of cosmids.
  2. Bacteriophages: Viruses that infect the different bacterias are kmown as bacteriophages. These viruses can be utilized as the vectors. Since they shows the following characters, they can be use as vectors:
  • They are capable of replicating in the suitable host cells.
  • They have fast propagating feature.
  • They are able to infect the host cell very effectively.
  • They are capable of growing in lytic phase too.

Steps involve in the Recombinant DNA Technology

Recombinant DNA technology involved with different steps for the perfect hybrid species. Here the targeted DNA is inserted in the vector DNA which is capable of replicating within the host cell for the proper cloning of specific DNA. Some steps involve in recombinant DNA technology are described below:

Source: fig: Diagrametic reprensentation of gene cloning
fig: Diagrametic reprensentation of gene cloning
  1. Preparation of gene: This is the first step that involve in this technology in which the foreign DNA is identified, isolated and prepared.
  2. Insertion of foreign DNA into plasmid: In this step, first the plasmid is cut with restriction enzymes which were used for the preparation of fragment of foreign DNA. Then the fragment of foreign DNA is attached with the plasmid covalently. The foreign DNA attached with the plasmid is known as the recombinant plasmids.
  3. Transformation of recombinant plasmid into host cell: This is the process of transformation of the recombinant plasmid into the host cell which is capable of proper DNA replication. As a result cloning of foreign DNA takes place within the host cells.
  4. Detection of the cloned DNA: This is the step which involve in the detection of the resulting DNA as well as the identification of resulting DNA. The resulting DNA may be useful or harmful, so it is necessary to detect the resulting DNA. But most of genes are remarkable. The formation DNA molecules is not 100% efficient, every vectors do not carry Foreign DNA. This step helps to separate the vector carrying foreign DNA and vectors not carrying foreign DNA.

Applications of recombinant DNA technology

Recombinant DNA technology has a great application in the present world. With the application of biotechnology gene transfers is possible in the present world. Any gene can be inserted in any body by the help of recombinant DNA technology.

This technology has brought so many opportunities for the manipulation of the genetic materials. This technology is able to produce different unrelated genes hybrids. This technology has various importances in different fields. Some of its importance in different field is described below:

Application in the field of genetic engineering in the field of medical science and human health

Genetic engineering has got a lot application in the field of medical science as well as human health. It is able to produce different medicines to cure different diseases. Different human diseases have got treatment with the help of this technology. Some of its other uses are as follows:

  1. Vaccines: This technology has been able to produce different vaccines which contain an antigen prepare from the parts or the whole organism causing the diseases. The produce vaccines use against the several antigens. This technology can produce clone of the gene for protective antigen protein.
  2. Human growth hormones: Now a day with the help of DNA recombinant technology several growth hormones are prepared commercially for the treatment of the dwarfism of human.
  3. Insulin: Insulin is the treatment against the diabetes. It is the protein hormone which helps to control the diabetes. With the help of the recombinant DNA technology it is possible to produce the human insulin bacterially which is called humulin and available in the market. Microbial products are safer to use than that of the products produced from traditional sources.
  4. Monoclonal antibodies: Simply antibodies are the protein produced by our body against the different specific antigens. With the help of hybridoma technology monoclonal antibodies can be synthesis artificially.( Copy pest)
  5. Antibiotics: Antibiotics are use by many people in the world to control different diseases. They are also use for to treat different animal’s diseases. Antibiotics are use for purpose of preservation of especially like fresh meat, fish and poultry feeds .Due to the use of antibiotics foods can be kept for longer period of time, since it prevent food from bacteria. Antibiotics are use in the sector of animal husbandry. They are use as animal feed because they help to enhance the growth of the animals.


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Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

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1. Recombinant DNA technology terms such as “gene surgery”, “gene manipulation”, “gene therapy”, “gene transplantation”, etc. commonly used.

2. Vector should be able to replicate inside the host cell.

3. Plasmids are the circular piece of DNA present in bacteria which has extra chromosome. 

4.  This technology has been able to produce different vaccines which contain an antigen prepare from the parts or the whole organism causing the diseases.

5. Microbial products are safer to use than that of the products produced from traditional sources.


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