The document discusses several molecular genetic techniques and genomics methods, including: 1) The polymerase chain reaction (PCR) can amplify a specific DNA sequence from a complex mixture using primers and repeated heating/cooling cycles. 2) Southern blotting allows detection of specific DNA fragments in a mixture by separating fragments by gel electrophoresis, transferring them to a filter, and using a radiolabeled probe. 3) Northern blotting similarly detects specific mRNAs and is used to analyze gene expression levels under different conditions.

2. Characterizing and Using Cloned DNA Fragments The Polymerase Chain Reaction Amplifies a Specific DNA Sequence from a Complex Mixture

18. Blotting Techniques Permit Detection of Specific DNA Fragments and mRNAs with DNA Probes

22. EXPERIMENTAL FIGURE 9-26 Southern blot technique can detect a specific DNA fragment in a complex mixture of restriction fragments. The diagram depicts three different restriction fragments in the gel, but the procedure can be applied to a mixture of millions of DNA fragments. Only fragments that hybridize to a labeled probe will give a signal on an autoradiogram. A similar technique called Northern blotting detects specific mRNAs within a mixture. [See E. M. Southern, 1975, J. Mol. Biol. 98:508.]