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A probe is a single-stranded sequence of DNA or RNA used to search for its complementary sequence in a sample genome. Probe sequences were hybridized to their complementary sequence. Because the probe is labeled with a radioactive or chemical tag that allows its binding to be visualized. In a similar way, labeled antibodies are used to probe a sample for the presence of a specific protein. Alpha lifetech Inc. provides a list of probes for rapid identification of a wide range of chromosomal aberrations across the genome.


DNA Probes


Long DNA probes can be generated using recombinant DNA techniques as inserts in plasmids. Linearization of plasmid DNA yields a DNA probe of several hundred to several thousand base pairs in length. DNA probes can be labeled with photoactivatable biotin or by any methods used to label analyte DNA.

Shorter DNA probes (less than B50 bases) are usually synthesized. A wide variety of labels are available as phosphonamidites for automated incorporation at 50, 30, or internal positions in the oligonucleotide. Alternately, amino or thiol groups can be introduced during synthesis. These reactive groups are available for linking to essentially any fluorophore or enzyme using crosslinking reagents.




RNA Probes


RNA probes bind tighter to their complementary strands than do DNA probes. Poor stability due to ubiquitous ribonucleases has hampered more widespread use of short RNA probes, as has the difficulty of efficient chemical synthesis of long RNA oligomers. Recent advances in RNA synthetic chemistry have solved the latter problem.

Long RNA probes are generated by in vitro transcription from linearized plasmid DNA containing a promoter sequence for a DNA-dependent RNA polymerase such as SP3, T3, or T7 polymerases. Commercially available kits for high-yield transcription with label incorporation are available. It is also technically trivial to introduce a T7 promoter sequence as a 50-extension of a PCR primer. Amplification introduces the promoter sequence into the amplicon. Transcription of the amplicon with T7 RNA polymerase and a modified NTP yields the labeled RNA probe. Shorter RNA probes (less than B50 bases) are chemically synthesized, and label is most conveniently introduced during.



Today, the most common used probe type is the accurately constructed bacterial artificial chromosome (BAC). Designing or selecting an appropriate FISH probe often requires a balance between sensitivity and specificity, i.e., a probe must be large enough to ensure specific binding and carry enough label for detection. On the other hand, as the length of the probe increases, so does the probability that the probe will hybridize to other target sequences. In addition, probes that are too long may produce large or diffuse signals.

In the research field, FISH can be used to identify the location of genes, determine the number and integrity of human chromosomes, and perform human chromosome karyotyping and chromosome painting. In clinical laboratories, FISH has become a standard tool for the detection of chromosomal aberrations, especially in prenatal and cancer diagnosis. At present, FISH probes and procedures for many genes have been analyzed and clinically validated, and more are being developed and tested.

Alpha Lifetech Inc. has been devoted to molecular biology and cytogenetics research for several years. Our scientists have the experience and knowledge to develop different types of fluorescence in situ hybridization (FISH) probes to meet the specific needs of our clients. We can custom synthetic double-stranded DNA probes, single-stranded DNA probes, RNA probes and oligonucleotide. From protocol development, probe design and synthesis, hybridisation detection to final data analysis, we have standard procedures and a comprehensive technical service system to ensure the high-quality FISH services to support clients' research needs.

For more information, please contact us and our technical support team will get back to you as soon as possible.



[1] Keller, G.H, Cumming, et al. Chemical method for introducing haptens on to DNA probes[J]. Anal. Biochem.; (United States), 1988, 170: 2.

[2] Iii M G. Sex-specific DNA probes,US5215884[P]. 1993.

[3] Siammour A, Blevins T, Meins F J. RNA PROBES. 2006.

[4] Lin D H, Wen-Duo Y E. The Application of In Situ Hybridization Technique with RNA Probes[J]. Letters in Biotechnology, 2007.