Applications of Nucleic Acid Hybridization

The high specificity of base-pairing interactions between two strands of DNA can be used to locate a specific nucleotide sequence in a sample (figure 9.6). Double-stranded DNA, when exposed to a high temperature or a high pH solution, will denature, or separate into two single strands. When the tem-

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Self-Annealing

Gene X (from Bacterium A)

9.2 Applications of Nucleic Acid Hybridization 225

Hybridization

Gene X (from Bacterium A)

Unknown gene (from Bacterium B)

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High temperature and/or a high pH solution denatures double-stranded DNA.

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Lowering the temperature and neutralizing the pH allows complementary strands to anneal.

Result: DNA from Bacterium A hybridizes to Bacterium B DNA.

Conclusion: Unknown gene from Bacterium B is homologous to gene X from Bacterium A. It is likely that the proteins encoded by the two genes have similar functions.

Figure 9.6 Nucleic Acid Hybridization Can Be Used to Locate Homologous Sequences perature is lowered and the pH is neutral, the two strands will anneal because of the base-pairing interactions of the complementary strands. Two complementary strands from different sources will also anneal, but the process may then be called hybridization to reflect the fact that each strand originated from a different source to create a hybrid molecule. Regions of double-stranded DNA in which the respective single strands hybridize to one another are homologous, or have similar or identical nucleotide sequences, and probably encode similar gene products.

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