Southern blots performed with restriction enzyme-digested genomic DNA may be used to determine the number of sequences (e.g., gene copies) in a genome.
The second diagram shows how this fragment size variation would look on a Southern blot, and how each allele (two per individual) might be inherited in members of a family.
The concepts of the Southern blot were used in the development and creation of the modern microarray slide, which is an extensively used experimental tool.