The key difference between DNA and RNA probes is that DNA probes are fragments of DNA that are complementary to target nucleotide sequences while RNA probes are stretches of single-stranded RNA which are complementary nucleic acid sequences of target sequences.
A probe is an artificially synthesized short sequence of DNA or RNA that could be labelled radioactively or with nonradioactive molecules. It can have a length of 100 to 1000 bases. Probes are useful in detecting target nucleotide sequences that are complementary to the sequence of the probe. Once added, probes get hybridized with the complementary sequences or the target sequences and make it visible to identify the target sequences since it carries radioactivity. Probes are important molecular tools for in many microbial and molecular areas such as detection of genetic diseases, in virology, in forensic pathology, in paternity testing, in DNA fingerprinting, RFLP, molecular cytogenetics, in situ hybridization, etc.
CONTENTS
1. Overview and Key Difference
2. What are DNA Probes
3. What are RNA Probes
4. Similarities Between DNA and RNA Probes
5. Side by Side Comparison – DNA vs RNA Probes in Tabular Form
6. Summary
What are DNA Probes?
DNA probes are single-stranded stretches of DNA. They can be used to detect the presence of complementary nucleic acid sequences (target sequences) by hybridization. Once a DNA probe hybridized with its complementary sequence, it forms a double-stranded hybrid. In order to detect them, DNA probes are generally labelled with radioisotopes, biotin, epitopes or fluorophores. The DNA probes labelled with biotin can be detected with streptavidin-labelled alkaline phosphatase by a number of enzymatic and chemical methods.
Figure 01: DNA Probe
The nucleotide sequence of the DNA probe is known. They are short sequences with a length of 100 to 1000 base pairs. Long DNA probes can be generated by recombinant DNA technology. They can also be generated by PCR and cloning. In clinical microbiology laboratories, DNA probes are readily available for the rapid diagnosis of infectious diseases.
What are RNA Probes?
RNA probes are single-stranded stretches of RNA. They are complementary sequences to target sequences in the sample. They are commonly synthesized with the RNA polymerases from bacteriophages SP6, T7, or T3 by in vitro transcription of DNA. Long RNA probes can be generated by in vitro transcription from linearized plasmid DNA. Generally, RNA probes bind strongly and tighter to their complementary sequences than DNA probes. Similar to DNA probes, RNA probes also can be labelled while they are being transcribed.
What are the Similarities Between DNA and RNA Probes?
- Both DNA and RNA probes are single-stranded nucleotide sequences.
- Both are artificially designed and synthesized.
- Moreover, they can be labelled with radioisotopes, epitopes, biotin or fluorophores.
- They have a strong affinity towards a specific DNA or RNA target sequence.
- They are used in various blotting and in situ hybridization techniques for the detection of target nucleic acid sequences.
- Both types of probes can be hybridized with their complementary sequences.
- They are also used in the identification of microorganisms and the diagnosis of infectious, inherited, and other diseases.
What is the Difference Between DNA and RNA Probes?
DNA probe is a short stretch of DNA which is complementary to the target sequence. On the other hand, the RNA probe is a short single-stranded stretch of RNA complementary to the target sequence. Thus, this is the key difference between DNA and RNA probes. Furthermore, DNA probes contain A, T, C and G while RNA probes contain A, U, C and G.
Moreover, a further difference between DNA and RNA probes is their thermodynamic stability. RNA probes show greater thermodynamic stability compared to DNA probes.
Below infographic tabulates the important differences between DNA and RNA probes.
Summary – DNA vs RNA Probes
A probe is a small fragment of DNA or RNA used to detect the presence of a specific sequence in the sample of DNA or RNA by molecular hybridization. DNA probes are short single-stranded DNA fragments while RNA probes are short single-stranded RNA sequences. They are known sequences. Thermodynamic stability is greater in RNA probes than DNA probes. RNA probes bind tightly to their complementary sequences than DNA probes bind. Thus, this summarizes the difference between DNA and RNA probes.
Reference:
1. “RNA Probe.” RNA Probe – an Overview | ScienceDirect Topics, Available here.
Image Courtesy:
1. “LightCycler Probes” (CC BY-SA 3.0) via Commons Wikimedia