Radioactive Labeling of Nucleic Acids and Autoradiography
Ultraviolet light absorption is a general method for detecting DNA, but does not distinguish between different DNA molecules. DNA can also be detected with radioactive isotopes During replication, radioactive precursors such as 32P in the form of a phosphate group and 35S in the form of phosphorothioate can be incorporated. Because native DNA does not […]
Restriction Enzymes
The ability to isolate, separate, and visualize DNA fragments would be useless unless some method was available to cut the DNA into fragments of different sizes. In fact, naturally occurring restriction enzymes or restriction endonucleases are the key to making DNA fragments. These bacterial enzymes bind to specific recognition sites on DNA and cut the […]
Gel electrophoresis
Gel electrophoresis followed by staining with ethidium bromide is used to separate DNA fragments by size . The gel of gel electrophoresis consists of agarose , a polysaccharide extracted from seaweed that behaves like gelatin. Agarose is a powder that dissolves in water only when heated. After the solution cools, the agarose hardens. For visualizing […]
DNA Isolation & purification
Basic to all biotechnology research is the ability to manipulate DNA. First and foremost for recombinant DNA work, researchers need a method to isolate DNA from different organisms. Isolating DNA from bacteria is the easiest procedure because bacterial cells have little structure beyond the cell wall and cell membrane. Bacteria such as E. coli are […]
Bacterial Transduction
It is also a mode of bacterial gene transfer, which is mediated by viruses. It is a frequent mode of horizontal gene transfer in nature. Indeed evidence suggests that the number of genes moved by marine viruses from one host cell to another is huge (perhaps 1024 per year). Furthermore, viruses in marine environments and hot […]
Bacterial Transformation
It is another way, DNA can move between bacteria is through transformation, discovered by Fred Griffith in 1928. Transformation is the uptake by a cell of DNA, either a plasmid or a fragment of linear DNA, from the surroundings and maintenance of the DNA in the recipient in a heritable form. In natural transformation, the […]
Bacterial conjugation
Conjugation, the transfer of DNA by direct cell-to-cell contact, depends on the presence of a conjugative plasmid. Plasmids are small, double-stranded DNA molecules that can exist independently of host chromosomes. They have their own replication origins, replicate autonomously, and are stably inherited. Some plasmids are episomes, plasmids that can exist either with or without being […]