GENETIC ENGINEERING
Genetic engineering can be defined as a collection of techniques that enables isolation of genes from one organism, clone them in another and have them expressed either in bacteria or order suitable organism in order to manufacture the protein encoded by the gene. Genetic Engineering is the creation of new DNA, usually by linking DNA from different organism together by artificial means using enzymes known as restriction enzymes.
The products of genetic engineering are known as gene cloning, recombinant DNA and the novel techniques that required in their production are collectively referred to as Recombinant DNA technology.
GENE CLONING
Gene cloning is the cultural process of genetic engineering that is used to reproduce large numbers of a specific gene, usually one that code for a desirable protein. The goal of cloning is to isolate a desired gene or segment of DNA from an organism and introduce it into a suitable host cell to obtain large quantities of DNA. Cloning is the production of many copies of the newly engineered DNA. The amplification of a specific cloned gene or genes, coupled with a marked increase in production of their protein products, makes it relatively easy to extract and purify these proteins in the laboratory.
Often this donor DNA is used for the large- scale production of important proteins, but the DNA may also be used in the detection of infectious agents or abnormal cells. Normally, the donor DNA is a small portion of the genome of a cell, and it is present as one or two copies in each cell. Therefore, before donor DNA can be extracted, a sufficient number of cells containing the desired DNA must be obtained, either from a small segment of tissue or by culturing the cells. The cells must then be disrupted and the genetic material extracted.
STEPS INVOLVED IN GENE CLONING
A gene of interest is first located and isolated directly from the strands of DNA that have been removed from the cells
This is done using a particular enzyme called restriction enzymes i.e an enzyme that can cut DNA molecules at specific nucleotides sequences.
Insertion of the gene i.e. DNA segment into the DNA of a suitable cloning vector, usually a plasmid or virus, that can enter a living cell where replication can occur under appropriate conditions.
The DNA formed by splicing DNA of the cloning vector with DNA of foreign gene is called recombinant DNA (rDNA). These two DNA are joined together by enzyme called ligase.
The rDNA is transferred into a host cell, where it will be replicated e.g. bacterium Escherichia coli. The host cell is placed in appropriate culture medium and allow to multiply.
The bacteria host cells are produced in millions, along with an equal or greater number of cloned genes.
By this, several copies of the gene of interest are produced. They are extracted from the host cells by treating the rDNA with restriction enzymes again.
To be continued with restriction enzymes in the next two days, stay tuned…