A collection of clones of chromosomal DNA, called a library, has no obvious order indicating the original positions of the cloned pieces on the uncut chromosome. To establish that two particular clones are adjacent to each other in the genome, libraries of clones containing partly overlapping regions must be constructed. These clone libraries are ordered by dividing the inserts into smaller fragments and determining which clones share common DNA sequences.
Credit or Source: Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science. science.energy.gov/ber/
Human Genome Program, U.S. Department of Energy, Genomics and Its Impact on Science and Society: A 2008 Primer, 2008. (Original version 1992, revised 2001 and 2008.) (website)