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 β-globin gene, which is found on human chromosome 11. A probe complementary to the β -globin gene binds to the β -globin gene and shows up as a brightly colored spot on human chromosome 11. In this way, researchers can detect where the β -globin gene is located within a set of chromosomes. Because the β -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 AluI sequence
B.A probe complementary to a tandemly repeated sequence near the centromere of the X chromosome

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