Identify nucleus acid based on ability of se chains with complementary base sequences to bind, hybridize, to each other. Hybridization can be dna-dna, dna-rna, or rna-rna (most common is dna-dna) Probe (single stranded labelled dna fragment) has a complementary sequence to the base sequence relying to detect. Nucleic acid sequence do not need to be perfectly complementary to be able to hybridize. Changing t (salt) and ph during hybridization can cause pairing of partially complementary sequences exhibiting numerous mismatched bases. Hybridization will occur between dnas related to one another. This approach is useful for identifying families of related genes. Bacterial enzymes > defend against foreign dna. Resulting dna pieces are called restriction fragments. Speci c recognition sequences is called a restriction site. Some cut both strand at same point > blunt ends. Some cut in a staggered manner > sticky ends. Genetic engineer can join dna fragments from different sources to make recombinant dna molecules.
