Question

How is bacterial transformation useful today?

Answer 1

Hint: There are several methods of introducing the ligated DNA into recipient cells. Recipient cells after making them 'competent to receive, take up DNA present in its surrounding Since DNA is a hydrophilic molecule, it cannot pass through cell membranes. In the condition that bacteria should take up the plasmid, the bacterial cells must first be made 'competent to take up DNA.

Complete answer:
The competence is usually started and completed by treating the cells with a defined concentration of a divalent cation, such as calcium, and this treatment increases the efficiency with which DNA enters the bacterium through pores in its cell wall.
 Possibly, calcium chloride causes the DNA to precipitate onto the outside of the cells or it may improve DNA binding.
1)Transformation : Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice. Followed by placing them briefly at 42°C (heat shock), and then putting them back on ice.
This enables the bacteria to take up the recombinant DNA. This method is transformation i.e., a procedure through which a piece of DNA is introduced into a host bacterium.
So, if a recombinant DNA bearing gene for resistance to an antibiotic (e.g., ampicillin) is transferred into E.coli cells, the host cells become transformed into ampicillin-resistant cells. If we spread the transformed cells on agar plates containing ampicillin, only transformants will grow, untransformed recipient cells will die.
In this way bacterial transformation helps today.
Since, one is able to select a transformed cell in the presence of ampicillin, the ampicillin-resistance gene in this case is called a selectable marker.

2)In another method known as microinjection, recombinant DNA is directly injected into the nucleus of an animal cell.

3)In another method, suitable for plants, cells are bombarded with high-velocity microparticles of gold or tungsten coated with DNA in a method known as biolistics or gene gun.

4)And the last method uses 'disarmed pathogen' vectors, which when allowed to infect the cell, transfer the recombinant DNA into the host. For example, Ti plasmid of Agrobacterium and Retroviruses.

5)Electroporation : Short electrical impulses of high field strength are given. These increase the permeability of protoplast membrane by creating transient microscopic pores, thus making entry of DNA molecules into the cells much easier

Note: 1. Genetic engineering can be used to create organisms with the desired traits.
2. Disarmed pathogens are used as vectors.
3. Plant varieties can be made to withstand high temperatures with the help of genetic engineering.