Principles of Biochemistry, Volume 3 - A. Lehninger 1985

Molecular Mechanisms of Genetic Information Transfer
DNA: Structure of Chromosomes and Genes
DNA strands from two different species can form DNA-DNA hybrids

If human and mouse DNA duplexes, isolated from their respective Cells, are thermally denatured separately, then mixed and incubated at 65°C for many hours, the majority of mouse DNA strands will “anneal” with complementary mouse DNA strands to reform the original duplex; similarly, most human DNA strands will reassociate with complementary human DNA strands. However, along with this, a certain number of single mouse DNA strands will bind to single human DNA strands, resulting in hybrid duplexes in which specific segments of mouse DNA form double-stranded regions with segments of human DNA. Base pairing occurs only between certain Regions of the human and mouse DNA strands; the remaining bases are unable to form complementary pairs. Hybrid duplexes form only if There is a certain degree of sequence similarity between the DNAs of the two different species. The closer the evolutionary relationship between two species, the greater the extent to which their DNAs will form hybrids. For instance, human DNA forms hybrids much more readily with mouse DNA than with Yeast DNA.

Hybridization assays (Fig. 27-15) are a powerful tool for investigating numerous aspects of biochemical genetics. They can be used not only to determine the genetic relatedness of two species, but also to link a specific DNA sequence to a given RNA through DNA-RNA hybridization. Furthermore, hybridization techniques are widely applied in the Isolation and Purification of genes and RNA.