Chapter 15, Problem 6P

How do you know if the halibut you purchased at the supermarket is really halibut? To identify the source of a biological sample, scientists PCR amplify and then sequence a region of DNA known to vary between species. For animals, this DNA region is a 648–base pair portion of the mitochondrial cytochrome oxidase I gene. The sequence of this mtDNA region acts as a so-called DNA barcode because a database exists that contains the sequences of this mtDNA region that are unique for hundreds of thousands of animal species.

a.	Why do you think that a region of mitochondrial DNA is used for barcoding animals, as opposed to a region of nuclear genomic DNA?
b.	A single pair of PCR primers can be used to barcode any species of fish. Explain how this is possible.
c.	List criteria that scientists would have considered when determining which mitochondrial DNA sequence to use for barcoding animals.