Using Cloned DNA Fragments to Study Gene Expression
Southern blotting, which can detect a single specific DNA fragment within a complex mixture, combines gel electrophoresis, transfer (blotting) of the separated bands to a filter, and hybridization with a complementary labeled DNA probe (see Figure 6-24). The similar technique of Northern blotting can detect a specific RNA within a mixture.
The presence and distribution of specific mRNAs can be detected in living cells by in situ hybridization.
DNA microarray analysis simultaneously detects the relative levels of expression of thousands of genes in different types of cells or in the same cells under different conditions (see Figure 6-26).
Cluster analysis of the data from multiple microarray expression experiments can identify genes that are similarly regulated under various conditions. Such co-
Expression vectors derived from plasmids allow the production of abundant amounts of a protein from a cloned gene.
Eukaryotic expression vectors can be used to express cloned genes in yeast or mammalian cells. An important application of these methods is the tagging of proteins with GFP or an epitope for antibody detection.