PCR: its principles and uses

PCR: Its principles and uses:-

•  PCR:- The process of multiplication of DNA segments using DNA polymerase and DNA primers is called PCR.

•  Discovery:- The PCR technique was discovered by Kary Mullis in 1985.

•  Thermocyclers are used to achieve different temperatures.

•  PCR has three main steps -

i. Denaturation:- When dsDNA is heated, both its chains separate at a temperature of 90°C.

ii. Primer Annealing:- Primers are attached at the 5 'end of single chains at a temperature of 55°C.

iii. Polymerization:- DNA polymerase enzyme polymerize the primers at 70°C temperature.

•  Heat stable DNA polymerase:-

Ø Normal DNA polymerase is heat sensitive. It is destroyed due to its deformation at 90°C temperature. Therefore, we cannot use normal DNA polymerase in PCR.

Ø Instead, we use heat stable DNA polymerase in PCR which can tolerate high temperature and does not deform.

Uses of PCR:-

i. The amplification of gene fragments as fast alternative of cloning. 

ii. The modification of DNA fragments. 

iii. The sensitive detection of pathogenic microorganisms, if desired followed by an accurate genotyping. 

iv. DNA analysis of arachaeological specimens. 

v. The detection of mutations relevant for inherited diseases, malignant transformation or tissue typing. 

vi. The analysis of genetic markers for forensic applications, for paternity testing and for the mapping of hereditary traits. 

vii. The species-specific amplification of DNA segments between interspersed-repeat elements. 

viii. The study of gene expression.