Genetics: Analysis and Principles 5th Edition by Robert Brooker

Exercise 40

In Chapter 22, the technique of fluorescence in situ hybridization (FISH) is described. This is another method for examining sequence complexity within a genome. In this method, a DNA sequence, such as a particular gene sequence, can be detected within an intact chromosome by using a DNA probe that is complementary to the sequence. For example, let's consider the -globin gene, which is found on human chromosome 11. A probe complementary to the -globin gene binds to the -globin gene and shows up as a brightly colored spot on human chromosome 11. In this way, researchers can detect where the -globin gene is located within a set of chromosomes. Because the -globin gene is unique and because human cells are diploid (i.e., have two copies of each chromosome), a FISH experiment shows two bright spots per cell; the probe binds to each copy of chromosome 11. What would you expect to see if you used the following types of probes
a. A probe complementary to the Alu I sequence
B. A probe complementary to a tandemly repeated sequence near the centromere of the X chromosome