Here's why:
* DNA is a double-stranded molecule: Each strand is composed of a sequence of nucleotides (adenine, guanine, cytosine, and thymine).
* Base pairing rules: Adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). This is called complementary base pairing.
* Hybridization: A labeled probe, which is a short single-stranded DNA sequence, can bind to its complementary sequence within a longer DNA molecule (the target gene) through these base pairing interactions.
In essence, the probe and target gene "recognize" each other based on their complementary nucleotide sequences, allowing them to bind together. This forms the basis of various techniques like Southern blotting, PCR, and DNA microarrays, which rely on hybridization for detection and analysis.
