17. Bacterial Genetics: Genetic engineering, DNA cloning, application of cloned DNA in molecular- Biological Genetic Methods in Diagnostics

Genetic Engineering / Recombinant DNA Technology

• Genetic engineering is also known as recombinant DNA technology or molecular DNA cloning.
• It involves the artificial and deliberate recombination of pieces of DNA from different organisms to create 'recombinant DNA'.
• The main idea is to transfer a gene of interest from its original cell into another DNA molecule (a vector, creating recombinant DNA), and then introduce this into a recipient cell to multiply the gene for specific purposes.
• Introducing recombinant DNA from a different species into a host organism makes that host transgenic.

Basic Components

• Cloning and Expression Vectors: Commonly plasmids and phages. These often contain antibiotic resistance genes for selection. Bacterial plasmids frequently function as vectors into which sequences to be cloned are inserted.
• DNA Sequence to be Cloned: The specific gene or DNA segment of interest. This DNA can come from bacteria, viruses, eukaryotic cells, or be chemically synthesized.
• Restriction Enzymes: Used to cleave DNA at specific recognition sites, producing 'restriction fragments'. These can have sticky ends or blunt ends. The same enzyme is used to cut the circular plasmid vector. Bacterial restriction endonucleases are invaluable tools in cloning.
• DNA Ligase: An enzyme used to link or join the fragments of donor DNA to the cloning vectors, creating the recombinant DNA molecule. Ligase makes the attachment permanent.
• Recipient Cells: Host cells, usually bacteria like E. coli, into which the recombinant DNA is introduced.