Molecular Biology of the Gene 7th Edition by Richard Losick, James Watson, Michael Levine, Tamara Baker, Alexander Gann

Exercise 7

In a biochemical experiment, you compare the products from splicing reactions carried out in vitro using three different substrates. In each case the substrate is a construct containing a single intron surrounded by two exons, and in all cases the construct is the same overall size. But in one case, the intron is a group I intron, in another a group II intron, and in the third an intron removed by the spliceosome. Each construct is labeled in a manner that allows it to be detected after gel electrophoresis, and each is tested in two reactions-one, conditions that support selfsplicing, and two, in the presence of nuclear extract as well. Match the intron type with the appropriate results (A, B, or C) in the gel shown below. Note that, for simplification, only the final products of the splicing reaction are seen, but before degradation of the introns.