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Home >>Molecular Probes and Gene Libraries >> Amplification of DNA Probe Signals
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Amplification of DNA Probe Signals - In recent years, DNA probe assays and immunoassays (using antibodies) have been competing with each other for a variety of purposes. While DNA probes have an advantage of detecting the presence of gene rather than its product, the immunoassay has the advantage of getting amplified target (the gene product) firstly due to transcription (several mRNA molecules can be synthesized on single copy of gene) and secondly due to translation (several protein molecules can be produced from same mRNA molecule).

The amplified target gives an amplified signal. Therefore, if DNA probes have to compete with monoclonal antibodies for immunoassay, DNA probe signals need to be amplified. Following devices have been used for the signal amplification:

(1) Probes have been developed for rRNA, since rRNA genes are present in thousands thus amplifying the target (as done by companies like Gene-Probe and Gene-Trak systems in USA).

2) Polymerase chain reaction (PCR) technology (which utilizes a thermostable polymerase) is used to generate millions of copies of target DNA sequence, which can then be identified by standard methods (Cetus Corp. in USA introduced this technique for more details consult next Chapter).

(3) Signal generating capacity of the probe can also be increased by any one of the following methods:

(i) concentrating more label at the site of target molecule by attaching multiple enzyme molecules to each of its DNA probe or

(ii) by using multiple probes, or

(iii) by attaching multiple enzymes to each of the multiple probes.

(4) Ampli probe technology uses multiple secondary probes (each having one or more enzyme molecules) that hybridize to multiple target specific primary probes. The secondary probe is independent of target, but helps 10 amplifying the signal.

These approaches have been described as Christmas Tree or Christmas Forest approaches.The above amplification systems will playa significant role in the use of DNA probes in future for a variety of purposes.

 
 

 
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