DNA being a hydrophilic molecule cannot pass through cell membrane. Hence, the bacterial cell is made competent to accept the DNA molecule. Thus, competency is the ability of a cell to take up foreign DNA.
Following methods are used to make a bacterial cell competent: the bacteria should be made competent to accept the DNA molecules, (i) Competency is the ability of a cell to take up foreign DNA. (ii) Methods to make a cell competent are as follow. (a) Chemical method In this method, the cell is treated with a specific concentration of a divalent cation such as calcium to increase pore size in cell wall.
The cells are then incubated with recombinant DNA on ice, followed by placing them briefly at 42°C and then putting it back on ice. This is called heat shock treatment.
This enables the bacteria to take up the recombinant DNA.
(b) Physical methods In this method, a recombinant DNA is directly injected into the nucleus of an animal cell by microinjection method. In plants, cells are bombarded with high velocity microparticles of gold or tungsten coated with DNA called as biolistics or gene gun method. (c) Disarmed pathogen vectors when allowed to infect the cell, transfer the recombinant DNA into the host.
Why a cell must be made competent to take up DNA?Explain the steps by which a bacterial cells made competent to take up plasmid/rDNA.
Answers
MR.JAGDEESH
DNA being a hydrophilic molecule cannot pass through cell membrane. Hence, the bacterial cell is made competent to accept the DNA molecule. Thus, competency is the ability of a cell to take up foreign DNA.
Following methods are used to make a bacterial cell competent:
the bacteria should be made competent to accept the DNA molecules,
(i) Competency is the ability of a cell to take up foreign DNA.
(ii) Methods to make a cell competent are as follow.
(a) Chemical method In this method, the cell is treated with a specific concentration of a divalent cation such as calcium to increase pore size in cell wall.
(b) Physical methods In this method, a recombinant DNA is directly injected into the nucleus of an animal cell by microinjection method. In plants, cells are bombarded with high velocity microparticles of gold or tungsten coated with DNA called as biolistics or gene gun method.
(c) Disarmed pathogen vectors when allowed to infect the cell, transfer the recombinant DNA into the host.