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Probes

Molecular DNA- or RNA-based probes are now routinely used in screening gene libraries, detecting nucleotide sequences with blotting methods, and in other gene technologies, such as nucleic acid and tissue microarrays.

Types of Probes
cDNA probes

cDNA probes can be double-stranded or single-stranded. Double-stranded are synthesized from a messenger RNA (mRNA) template in a reaction catalysed by the enzyme reverse transcriptase. Single-stranded are prepared by PCR with single antisense primer extension and Taq polymerase.

RNA probes

RNA probes or riboprobes are synthesized by using cDNA as a template.

Oligonucleotide probes

Oligonucleotide probes are a single-stranded of DNA ranging in size from 20 to 50 bases and can be generated with an automated DNA synthesizer.

  • Great flexibility in the choice of probe by using appropriate primers.

  • Can be labeled to high specific activity (most sensitive).

  • Can detect low numbers of gene expression. 

  • Can penetrate cells more readily than other probes.

  • Can produce excellent hybridization signals.

  • Labeled cRNA are unstable.

  • Less sensitive than longer cDNA or cRNA probes 

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