Genetic engineering
Genetic engineering deals with the manipulation of genes. It refers to the artificial synthesis, modification, removal, addition and repair of the genetic material(DNA) to get a desired and useful phenotype. In this technique the DNA or genes of different origins are joined to produce a hybrid DNA called recombinant DNA. The science of genetic engineering is in its infancy.
Tools used in genetic engineering
The following tools are used in genetic engineering:
- Host
- Vector
- Desired DNA and
- Enzyme
Host is a cell where the recombinant DNA is allowed to multiply to produce thousands of copies. Bacteria, yeasts, etc. are used as hosts. Among bacteria Escherichia coli is used extensively as the host.
2) Vector
Vectors are the vehicles which are used to transfer the foreign DNA from one cell to another. The commonly used vector is the plasmid. It is an single, circular, double stranded extra chromosomal, self replicating DNA present in bacterial cells.
3) Desired DNA
It is the DNA to be cloned and transferred. It can either be synthesized artificially or be obtained from other cells. example Nitrogen fixing gene(NiF gene), insulin genes, etc.
4) Enzymes
Enzymes are used in genetic engineering as chemical knives and sutures. They are used to cut and link DNA molecules at specific site. There are two types of enzymes, namely restriction endonucleases and ligases
a) Restriction endonucleases: These enzymes are used as chemical knives. They cut DNA strands. These enzymes produce staggered cuts and the resulting fragments terminate in short single stranded projections called sticky ends. They are commonly known as molecular scissors. The important endonucleases are as follows: EcoR1, Hind III, Bam I, hae III etc.
b) Ligases: These are used as chemical sutures. They link the cut ends of DNA strands. The fragments which have annealed together have nicks which can be covalently sealed by this enzyme.