Brief Introduction To DNA Probes

DNA probes help scientists to detect a specific gene in a long DNA sequence. According to Dr. Michael A. Pfaller, DNA probes are “single-stranded pieces of nucleic acid, labeled with a specific tracer (isotope, enzyme, or chromophore), that will hydrogen bond (hybridize) with complementary single-stranded pieces of DNA (or RNA) under the appropriate conditions of pH, temperature, and iconic strength.”

The Foundation for Genomics and Population Health website has a helpful video about hybridization where it explains that hybridization “refers to the process in which two complementary pieces of DNA (or a piece of DNA and a piece of RNA) anneal to form a double-stranded molecule.” It further reports that the piece of DNA or RNA is referred to as a probe.

To prepare a DNA probe in a laboratory, the steps consist of the following:

— Identify unique DNA (or RNA) sequences
— Isolate those sequences
— Reproduce the sequences in sufficient quantities
— Label them with a tracer or reporter molecule to allow detection in hybridization.

Preserve Articles explains that to produce a DNA probe, a scientist can use one of three methods:

— Use a template DNA with the help of purified biological enzymes
— Obtain by using automated DNA synthesizers
— Include in viral and bacterial DNA, allowing many copies of DNA probe can be obtained when virus or bacteria replicate.

It further states that the DNA probe assay, which is a test to identify the constituent elements and quality of the DNA, consists of several steps including:

— Sample to be tested is treated with detergents and enzymes to remove non-DNA components.
— Then DNA is denatured using low pH.

Single stranded DNA binds on filters and is exposed to excess of DNA probes but only one of these will hybridize.

At the same time unbound DNA is detected by a variety of available methods using florescence and dye etc.

To denature a DNA probe, a scientist must heat it up, which then causes the double-stranded helix to separate into two individual strands without breaking the chemical bonds between the individual bases in the chain. Once this happens, one must cool the separated probe down, add the labeling (usually done with fluorescent or radioactive molecules), and then one can study the probe.

The DNA probe can provide diagnosis of infections and disease, identify food contaminants for isolation of genes, and determine the presence of microbial species. Because a DNA probe is used to find specific sequences of nucleotides in a DNA molecule, they have provided “medical and veterinary diagnostic laboratories with powerful new tools to enhance the diagnosis of infectious diseases, genetic disorders, and malignancies, as well as more sensitive and specific means to accomplish such tasks as tissue typing and paternity testing” writes Dr. Pfaller.

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