Genetic engineering can be defined as the science of adding, removing or replacing genetic units in order to achieve permanent and heritable changes in plants and animals for the benefit of mankind. Terms such as “gene surgery”, “gene therapy”, “gene manipulation”, “gene transplantation”, etc. have been synonymously used with genetic engineering. Basically the term genetic engineering refers to techniques that are used to manipulate, move, recombine and propagate DNA.
A detailed knowledge of the molecular nature of the gene and ability to manipulate cells of higher organisms as well as bacteria may eventually allow the possibility of genetic engineering. It has been very useful in plants and animals and has brought biological revolution. Luciferase gene from firefly has been introduced in tobacco plant enabling scientists to study the activation of genes of genes of their choice by measuring the light emitted by the plants. Introduction of nitrogen fixation gene (NIF gene) and Bt gene in cereals are really a boon in agriculture. In human being, genetic engineering is being used for diagnosis of hereditary diseases and thus has bright prospects to be used for gene therapy.
Genetic engineering provides great promises for the improvement of crop plant. Genetically engineered crops with better nutritional status, resistance to insects, pets and herbicides, resistance to fungal, bacterial and viral diseases and resistance to environmental stresses have shown a great potential. The techniques of biotechnology have already increased the capacity to enhance plant productivity. Similarly it has tremendous impact on medicine for diagnosis and treatment of many diseases.
Cloning of DNA
In gene cloning, firstly the DNA of an organism containing the gene of interest in cut into smaller pieces. This gene is called target gene or foreign DNA.
Secondly, the target DNA is joined (in vitro) to a second piece of DNA that can replicate itself and attach any target DNA. This second DNA is often called vector or cloning vehicle. The result of the joining is a hybrid molecule, a hybrid or recombinant DNA
Thirdly, the jointed target and vector is then introduced into a living cell. The cell serves as a biological copying machine, making many exact copies of recombinant molecule. This all process is called molecular cloning.
Tools of gene cloning
Cloning is a basic step in recombinant DNA technology. It involves incorporation of a piece of foreign DNA into a vector. Following tools are needed for cloning of DNA:
a) Restriction endonucleases or enzymes – These enzymes cleave double stranded DNA into smaller fragments. They cut the DNA at specific sites. They are popularly known as molecular scissors.
Restriction enzymes are isolated from bacteria and are named for the bacteria from which they are derived. About hundreds of different restriction enzymes have been isolated. The best known example of a restriction enzyme is EcoR1. These enzymes are highly specific and recognized specific sequences in double-stranded DNA and make two sequence-specific cuts, one in each strand. The most commonly used restriction endonucleases.
b) DNA ligase – DNA ligase is used to covalently link the 3’ – hydroxyl end of one strand of DNA to the 5’ – phosphate ends of second strand. Therefore, DNA segments that are cut by restriction endonucleases can be ligated or joined by DNA ligas enzyme.
c) Vectors – for cloning, a vector is an essential tool in which the foreign gene is inserted. They are also known as cloning vehicles. Vectors must have the following features:
i. They must be able to replicate within the host cell.
ii. They must be capable of insertion into the host cell.
iii. They must have a selectable marker.
iv. They must contain a site for insertion of foreign DNA. In order to carry foreign DNA into cell, the vector must be linked to the foreign DNA.
A detailed knowledge of the molecular nature of the gene and ability to manipulate cells of higher organisms as well as bacteria may eventually allow the possibility of genetic engineering. It has been very useful in plants and animals and has brought biological revolution. Luciferase gene from firefly has been introduced in tobacco plant enabling scientists to study the activation of genes of genes of their choice by measuring the light emitted by the plants. Introduction of nitrogen fixation gene (NIF gene) and Bt gene in cereals are really a boon in agriculture. In human being, genetic engineering is being used for diagnosis of hereditary diseases and thus has bright prospects to be used for gene therapy.
Genetic engineering provides great promises for the improvement of crop plant. Genetically engineered crops with better nutritional status, resistance to insects, pets and herbicides, resistance to fungal, bacterial and viral diseases and resistance to environmental stresses have shown a great potential. The techniques of biotechnology have already increased the capacity to enhance plant productivity. Similarly it has tremendous impact on medicine for diagnosis and treatment of many diseases.
Cloning of DNA
In gene cloning, firstly the DNA of an organism containing the gene of interest in cut into smaller pieces. This gene is called target gene or foreign DNA.
Secondly, the target DNA is joined (in vitro) to a second piece of DNA that can replicate itself and attach any target DNA. This second DNA is often called vector or cloning vehicle. The result of the joining is a hybrid molecule, a hybrid or recombinant DNA
Thirdly, the jointed target and vector is then introduced into a living cell. The cell serves as a biological copying machine, making many exact copies of recombinant molecule. This all process is called molecular cloning.
Tools of gene cloning
Cloning is a basic step in recombinant DNA technology. It involves incorporation of a piece of foreign DNA into a vector. Following tools are needed for cloning of DNA:
a) Restriction endonucleases or enzymes – These enzymes cleave double stranded DNA into smaller fragments. They cut the DNA at specific sites. They are popularly known as molecular scissors.
Restriction enzymes are isolated from bacteria and are named for the bacteria from which they are derived. About hundreds of different restriction enzymes have been isolated. The best known example of a restriction enzyme is EcoR1. These enzymes are highly specific and recognized specific sequences in double-stranded DNA and make two sequence-specific cuts, one in each strand. The most commonly used restriction endonucleases.
b) DNA ligase – DNA ligase is used to covalently link the 3’ – hydroxyl end of one strand of DNA to the 5’ – phosphate ends of second strand. Therefore, DNA segments that are cut by restriction endonucleases can be ligated or joined by DNA ligas enzyme.
c) Vectors – for cloning, a vector is an essential tool in which the foreign gene is inserted. They are also known as cloning vehicles. Vectors must have the following features:
i. They must be able to replicate within the host cell.
ii. They must be capable of insertion into the host cell.
iii. They must have a selectable marker.
iv. They must contain a site for insertion of foreign DNA. In order to carry foreign DNA into cell, the vector must be linked to the foreign DNA.
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