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The process of identifying specific DNA sequences by using DNA or RNA probes is called nucleic acid hybridization.
- Probes are defined as short strands of labeled oligosaccharide sequences.
- These can be used in DNA sequencing, microarray, polymerase chain reaction, hybridization, etc.
- The probes are of two types: radioactive probes and non-radioactive probes.
Radioactive probe and Non-radioactive probe
What is a Radioactive Probe?
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A radioactive probe is defined as a single-stranded DNA or RNA consisting of a radioactive tag.
- Radioisotopes of sulfur-35 and phosphorus-32 are used to label the radioactive probes.
- These isotopes are added to the probe molecule such that it can be tracked through radiation.
- Radioactive probes are used in the detection of cancerous cells and mutated genes.
What is a Non-Radioactive Probe?
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A non-radioactive probe is defined as a single-stranded DNA or RNA consisting of a chemical tag.
- Fluorescent molecules like biotin, fluorescein, and digoxigenin are also used.
- These probes are used in western blotting and immunoassay techniques.
- Non-radioactive probes give quick results and are less expensive than radioactive ones.
Differences between Radioactive and Non-Radioactive Probe
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The difference between radioactive and non-radioactive probes depends on cost, type of isotope, safety, harmful materials used, uses, etc. The following table shows the difference between the two:
| Parameters | Radioactive Probe | Non-Radioactive Probe |
|---|---|---|
| Definition | Probes which are labeled with radioactive tags | Probes which are labeled with chemical tags |
| Isotopes | They are labeled with radioactive isotopes like sulfur and phosphorus | They are labeled with chemicals like biotin |
| Safety | Not safe to use | Safe to use |
| Cost | Expensive | Less expensive than radioactive probes |
| Harmful materials used | Harmful materials are used | No harmful materials are used |
| Applications | Uses: Detection of cancerous cells | Uses: Cloning |
Things to Remember
- Radioactive and nonradioactive probes are used in nucleic acid hybridization.
- The safest probe labeling technique is biotin probe labeling.
- Probes that use radioactivity have a shorter half-life.
- The length of the molecular probes is 15-10000 bp long.
- Applications of these probes include gene expression, cell functioning, microarray, etc.
Sample Questions
Ques. What does biotin labeling mean? Is it considered a form of radioactive probing (2 marks)
Ans. Biotin labeling involves the use of biotin, as a probe
- Biotin labeling refers to attaching a biotin tag to the probe.
- It is a cheap and secure method.
- Biotin probes are highly accurate and sensitive.
Ques. Mention any three benefits of a non-radioactive probe. (2 marks)
Ans. The following are the three benefits of a non-radioactive probe.
- They have a longer shelf life.
- These probes are cost-effective.
- It is used to monitor pollutants in the environment
Ques. What are the applications of DNA probes? (3 marks)
Ans. The following are the applications of DNA probes.
- Identifying gene mutations.
- Identifying criminals through DNA fingerprinting.
- DNA replication by polymerase chain reaction.
- Contributing to gene regulation and gene mapping.
Ques. Enlist the types of probes utilized in molecular biology. (2 marks)
Ans. The following are the types of probes utilized in molecular biology:
- Fluorescent probes
- Radioactive probes
- Chromogenic probes
- Enzymatic probes
Ques. How should radioactive probes be handled with precaution? (2 marks)
Ans. When dealing with probes it is important to observe the following precautions:
- Ensure disposal of radioactive probes.
- The use of gloves and eye shields is mandatory.
Ques. What are the things we need to consider while using radioactive and nonradioactive probes? (2 marks)
Ans. The following things need to be considered by using radioactive and nonradioactive probes:
- The probes should be single-stranded.
- They must be complementary to the target gene.
- There should be a tag or a label present
Ques. Answer the following questions: (2 marks)
- How many nucleotides are found in a DNA probe?
- What is meant by nucleic acid hybridization?
Ans. a) The length of the typical DNA probe is about 20 – 1000 nucleotides.
b) Nucleic acid hybridization means a method of detecting a DNA sequence. There exist Northern and Southern blotting as two methods of nucleic acid hybridization
Ques. Write two uses of radioactive isotopes. (2 marks)
Ans. The following are the uses of radioactive isotopes:
- It is used in industries to measure the thickness of plastics or metal.
- They are used to identify defects in machines.
Ques. What is meant by the term “half-life” in radioactivity? (2 marks)
Ans. A half-life is defined as the time interval needed for the disintegration of a radioactive sample per second to decrease by one-half. Having a shorter half-life is one of the disadvantages of radioactive isotopes.
Ques. Name a radioactive isotope used in radiotherapy. (2 marks)
Ans. Iodine-129, Iodine-131, Uranium- 235, Tritium Carbon-14, Thronium-232, Plutonium-239, Xenon-135, Radon-222, and Cobalt-60 are examples of radioactive isotopes used in radiotherapy.
Ques. Which kind of probe is commonly used in Fluorescence in situ hybridization (FISH)? (2 marks)
Ans. Fluorescence in situ hybridization (FISH) is a laboratory technique that is used to find and recognize specific sequences of DNA. The non-radioactive probe is commonly used in FISH for:
- Detecting chromosomal abnormalities.
- Gene mapping.
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