Transformation techniques in biotechnology

preface

Simply gene alteration or modification is known as transformation.

Frederick Griffith 1928 acknowledged genetic transformation in bacterial strains.

Cell that can be used in transformation is called as competent.

( The bacterial cells that can take up the foreign DNA from the surroundings by a process called transformation are known as competent cells ) 

There are two types of transformation

1. Natural transformation:  ds DNA binds to the plasma membrane. Then enzymes cut the DNA and break the one strand of dna. After that protein binds to the dna and then this dna replaces the portion of bacterial dna.

Conjugation: Genetic exchange between two bacterial cell in direct contact 

Transduction: Genetic exchange through a vehicle Like plasmid or vector ( by bactriophage virus into the host bacterium )

• Agrobacterium mediated gene transfer: It is the stable technique of gene transfer.

2. Artificial transformation : It involves chemical,physical and enzymatic treatments. Artificial transformation can be induced in laboratory procedures that involve making the cell  penetrable to DNA by exposing it to conditions that do not normally occur in nature.

Chemically competent cells : 

It can be done by calcium choride treatment under cold condition for the attachement of the plasmid dna.

Then it is exposed to the heat shock which opens the pores of the cell membrane.

But the mechanism of uptake of dna by this transformation method is not clear.

Electrocompetent cells : 

In this method cells are shocked with the electric field which is to create holes in the cell membrane through which plasmid dna may enter the cell. After electric shock the holes are rapidly closed by cell membrane repair mechanism.

Basic procedure of Transformation:

Isolation of naked DNA : The cells are broken and the dna is released. The dna is 

subsequently isolate and collected.

Mixing of DNA to competent cells: The naked donor DNA is incubated with the

 competent recipient cells to which it binds.

Uptake and Recombination of Donor DNA: Donor DNA binds to competent recipient cells, then it enters the recipient cells. Portions of the donor DNA align, at random, with genes on the recipient DNA and segments of the two DNA are exchanged. This exchange inserts Donor genes into the recipient cells DNA.

REFRENCES:

http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/Chap9.html#Transformatio n• http://medicine.jrank.org/pages/2890/Transformation-Discovery- Transformation.html• http://www.sci.sdsu.edu/~smaloy/MicrobialGenetics/topics/transformation/•