Transformation And Transduction – Transfer Of Genetic Material

Genetic material can be transferred from one bacterial cell to another in very easy manner. It can also be performed in laboratory and may be observed in natural conditions. There are two methods those are studied very frequently and used to transfer genetic material (DNA) from one cell to another in laboratory under controlled condition. As it occur in nature as well, so it shows effective results as it happens naturally.

Transformation

It was the first example of genetic exchange in bacteria to have been discovered.

Transformation is the transfer of genetic information through the agency of free DNA.

Griffith in 1928 found that mice died when injected with a mixture of live no capsule ted (R) pneumococci and heat killed capsulated (S) pneumococci, neither of which separately proved fatal.

If in the experiment, the live (R) pneumococci were derived from casualties type II and the killed (S) strain from type III, from the blood culture of the mice those had died. Live III type capsulated pneumococcus could be isolated, showing that some factor in the heat killed type III pneumococcus had transferred the information from capsule synthesis to the live rough strain. Such transformation was subsequently demonstrated in vitro also. The nature of the transforming principle was identified as DNA by Avery, Macleod and McCarty in 1944.

Transduction

The transfer of the portion of DNA from one bacteria to another by a bacteriophage is known as transduction.

Bacteriophages are virus those parasite bacteria and and consist of nuclei acid core and a protein coat. During the assembly of bacteriophage inside bacteria, packaging error may occur, occasionally. A phase particle may have a segment of host DNA along with its own nucleic acid core. When this type of phage infect another bacteria, first bacteria’s DNA segment reaches to the another bacteria.

DNA transfer is effected and the recipient cell acquires new characters coded by the diner DNA.

Transduction may be ‘generalized’, when it involve any segment of donor DNA at random. Or it may be ‘restricted’, when a specific transducer only a particular genetic trait.

Reference
TextBook of Microbiology