Advanced Diagnostic AIDS
Write short note on DNA probe.
Or
Write in detail about advance diagnosis aids in periodontium.
Answer. DNA probes or deoxyribonucleic acid probe:
DNA probes are the advanced diagnostic aids in the microbiological diagnosis.
Probe Design
- DNA probes entails segments of single stranded nucleic acid, labeled with an enzyme.
- A radioisotope, that can be locate and bind to their complementary nucleic acid sequence with low cross reactivity to non-target organisms.
Read And Learn More: Periodontics Question And Answers
Types
- Whole genomic DNA probe.
- Closed DNA probe.
- Synthetic oligonucleotide probe.
Whole Genomic DNA
Whole genomic DNA probes are more likely to cross reaction with nontarget microorganisms due to the presence of homologous sequences between different bacterial species.
Oligonucleotide Probe
Oligonucleotide probes display limited or no cross-reactivity with non-target microorganism.
DNA Probe Procedure
- The plaque is first denaturated to obtain single strain bacterial DNA and then incubate on a membrane such as nitrocellulose. These single stands are individually labeled with a radioactive isotope.
- Specific-labeled DNA probe is incubated on the membrane to allow hybidrization, and then washed off to remove any unhybridized strands.
- The plaque sample contains complementary DNA; hybridization of 2 single strains takes place. It is covered with a radiographic plate.
- The radioactive labels create spots on the film, which are read with a densitometer.
- The darkness and size of the spots indicate the concentration of microorganisms present in the given sample.
DNA Probe Advantages
Sensitivity and specificity of probe are not affected by the presence of unrelated bacteria in the mixed culture sample.
DNA Probe Limitations
Probes are able to detect as few as 102-104 bacteria.
DNA Probe Commercial Kit
Omnigene is the commercially available DNA probe kit for assessment of number of subgingival bacteria.
STEPS IN MICROBIAL DIAGNOSIS WITH DNA PROBE
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