A PCR (Polymerase Chain Reaction) is one of the great and most widely used to technique in molecular biology. and has wide range of applications in medical and clinical laboratories for diagnosis purposes and this technique is widely and most commonly used in biological or bio medical research.
But, there are many types of PCR which have different applications and different levels of sensitivity. Some of the types of PCR are listed below with brief explanation.
Ligation-Mediated PCR: uses small DNA oligo nucleotide linkers (or adaptors) which are first ligated to DNA fragments of the target or template DNA.
Reverse Transcription PCR: a reverse transcription enzyme called "reverse transcriptase" which will amplify the RNA strand to DNA strand called cDNA (complementary DNA). In simple terms, this type of PCR generates complementary DNA Strands from a template RNA Strands. Hence the name "Reverse Transcription".
Multiplex PCR: Uses several pairs of primers annealing to different target sequences.
Asymetric PCR: It preferentially amplifies one strand of the target DNA.
Nested PCR: Two sets of primers are used in two successive reactions. In the first PCR, one pair of primers is used to generate DNA segments, which may contain segments amplified from non-target areas. The products from first PCR are then used as template in a second PCR, using one or two different primers whose binding sites are located within the first set which will eventually increase the sensitivity. Basically, this type of PCR is used to increase the specificity of DNA amplification.
VNTR PCR: it stands for "Variable Number of Tandem Repeats" PCR. this type of pcr is used to target the areas of the genome that exhibit length variation.
Methylatoin-Specific PCR: Used to identify the patterns of DNA methylation at cytosine-guanine (CpG) islands in genomic DNA.
Quantitative PCR: used to measure the specific amount of target DNA or RNA in a sample.
Touchdown PCR: the annealing temperature is gradually decreased in later cycles.
Hot-Start PCR: manually performed by heating the reaction components to the DNA melting temperatures i.e. 95C before the addition of polymerase enzyme.
Colony PCR: bacterial colonies are screened directly by the PCR. for example, screening the correct DNA segment in a vector constructs.. (The vector which has the target DNA is first transformed into bacteria, after colonies are formed, these colonies are directly used for the PCR).
Real-Time PCR: In this type of PCR, amplification of the target DNA segment is monitored in real-time. Not at the end like conventional PCR. Fluorescent molecules are used. commonly used are SYBR Green and TaqMan.
Assembly PCR: Synthesis of long DNA structures by performing PCR on a pool of long oligonucleotides with short overlapping segments, to assemble two or more pieces of DNA into one piece.
Other than these, there are variety of types of PCR which have specific application depending on the their sensitivity and requirements.
Asymetric PCR: It preferentially amplifies one strand of the target DNA.
Nested PCR: Two sets of primers are used in two successive reactions. In the first PCR, one pair of primers is used to generate DNA segments, which may contain segments amplified from non-target areas. The products from first PCR are then used as template in a second PCR, using one or two different primers whose binding sites are located within the first set which will eventually increase the sensitivity. Basically, this type of PCR is used to increase the specificity of DNA amplification.
VNTR PCR: it stands for "Variable Number of Tandem Repeats" PCR. this type of pcr is used to target the areas of the genome that exhibit length variation.
Methylatoin-Specific PCR: Used to identify the patterns of DNA methylation at cytosine-guanine (CpG) islands in genomic DNA.
Quantitative PCR: used to measure the specific amount of target DNA or RNA in a sample.
Touchdown PCR: the annealing temperature is gradually decreased in later cycles.
Hot-Start PCR: manually performed by heating the reaction components to the DNA melting temperatures i.e. 95C before the addition of polymerase enzyme.
Colony PCR: bacterial colonies are screened directly by the PCR. for example, screening the correct DNA segment in a vector constructs.. (The vector which has the target DNA is first transformed into bacteria, after colonies are formed, these colonies are directly used for the PCR).
Real-Time PCR: In this type of PCR, amplification of the target DNA segment is monitored in real-time. Not at the end like conventional PCR. Fluorescent molecules are used. commonly used are SYBR Green and TaqMan.
Assembly PCR: Synthesis of long DNA structures by performing PCR on a pool of long oligonucleotides with short overlapping segments, to assemble two or more pieces of DNA into one piece.
Other than these, there are variety of types of PCR which have specific application depending on the their sensitivity and requirements.
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