Purification of DNA from living cells
he genetic engineer will, at different times, need to prepare at least three distinct kinds of DNA.
Firstly, total cell DNA will often be required as a source of material from which to obtain genes to be cloned.
Total cell DNA may be DNA from a culture of bacteria, from a plant, from animal cells, or from any other type of organism that is being studied. It consists of the genomic DNA of the organism along with any additional DNA molecules, such as plasmids, that are present.
The second type of DNA that will be required is pure plasmid DNA. Preparation of plasmid DNA from a culture of bacteria follows the same basic steps
as purification of total cell DNA, with the crucial difference that at some stage the plasmid DNA must be separated from the main bulk of chromosomal DNA also present in the cell.
Finally, phage DNA will be needed if a phage cloning vector is to be used. Phage DKA is generally prepared from bacteriophage particles rather than from infected cells, so there is no problem with contaminating bacterial DNA.
However, special techniques are needed to remove the phage capsid. An exception is the double-stranded replicative form of M13, which is prepared from E. coli cells in the same way as a bacterial plasmid.
Sources:
Content:
Gene Cloning and DNA Analysis, an introduction(fifth edition), T. A. Brown