(a) Why should a bacterium be made 'competent'?
(b) Explain the role of 'microinjection' and 'gene gun' in biotechnology.
a) DNA is a hydrophilic molecule, it cannot pass through cell membranes. In order to force bacteria to take up the plasmid, the bacterial cells must first be made ‘competent’ to take up DNA. This is done by treating them with a specific concentration of a divalent cation, such as calcium, which increases the efficiency with which DNA enters the bacterium through pores in its cell wall. Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them briefly at (heat shock), and then putting them back on ice. This enables the bacteria to take up the recombinant DNA.
b) Micro-injection- Recombinant DNA is directly injected into the nucleus of an animal cell.
Gene gun- In plants, cells are bombarded with high-velocity micro-particles of gold or tungsten coated with DNA. This method is also known as Biolistics.