Evolution deals with heritable changes in populations over time. Because DNA is the molecule of heredity, evolutionary changes will be reflected in changes in the base pairs in DNA. Two species that have evolved from a common ancestor will have DNA that has very similar base pair sequences. The degree of relatedness of two species can be estimated by examining how similar their base pair sequences are. One method of assessing relatedness uses hybridization of DNA.

In the molecular genetic technique of hybridization of DNA, single strands of DNA from two different species are allowed to join together to form hybrid double helices. These hybrid segments of DNA can be used to determine the evolutionary relatedness of organisms by examining how similar or dissimilar the DNA base pair sequences are.

The technique of DNA hybridization is based on two principles: the first, that double strands of...