The Premise
Recombinant DNA (rDNA) molecules are DNA molecules formed by genetic recombination in a lab to bring together genetic material from multiple sources. This creates sequences of DNA that would not otherwise be found in biological organisms. Recombinant DNA molecules are also called chimeric DNA.
Recombinant DNA is possible because DNA molecules from all organisms share the same biochemical units (nucleotides).
Recombinant DNA (rDNA) is made by combining DNA from two or more sources. In practice, the process involves combining the DNA of different organisms. It depends on the ability to cut and re-join DNA molecules at points which are identified by specific sequences of nucleotide bases called restriction sites. |
|
DNA fragments are cut out of their normal position in the chromosome using restriction enzymes (also called restriction endonucleases) and then inserted into other chromosomes or DNA molecules using enzymes called ligases.
Bacteria as Vectors
|
The hereditary information of humans are stored in structures called chromosomes. The hereditary information of bacteria are stored in their bacterial chromosomes as well as on ring-like structures called plasmids. |
Plasmids naturally exist in bacterial cells, and they also occur in some eukaryotes. Often, the genes carried in plasmids provide bacteria with genetic advantages, such as antibiotic resistance. When a bacterium divides, all of the plasmids contained within the cell are copied such that each daughter cell receives a copy of each plasmid. Bacteria can also transfer plasmids to one another through a process called conjugation, which enable entire colonies of bacteria to survive.
|
Scientists have taken advantage of plasmids to use them as tools to clone, transfer, and manipulate genes. Plasmids that are used experimentally for vectors. Researchers can insert DNA fragments or genes into a plasmid vector (basically just a plasmid taken from a bacterium), and create a recombinant plasmid. This plasmid can be introduced into a bacterium. Then, because bacteria divide rapidly, they can be used as miniature factories to copy DNA fragments in large quantities. |