high density of repetitive sequences in complex genomes. Individual clones are 

 fingeqjrinted using a combination of restriction enzyme digestions followed hv 

 hybridization with selected classes of repetitive sequences. Along with information on 

 the lengths of all restriction fragments, the occurrence of repeat sequences is acquired 

 by image capture. With this fingerprinting data, overlapping cosmid clones are 

 identified. Cosmid clones obtained from tlow-sorted chromosome 16 were used to 

 identify 2261 individual clones arrayed in 389 contig sets — approximately one-half of 

 chromosome 16. The approach of "nucleating" at specific regions in the human genome 

 and exploiting the high density of interspersed repetitive sequences in human DNA 

 allows ( 1 ) rapid progress in early contig mapping phases that have generated large 

 (>100 kb) contigs and (2) the production of a contig map with landmarks useful for 

 rapid integration of the genetic and physical maps. 



Telomeric 

 Repeats 



Single Multigene 

 Copy Families 

 Genes 



Centromere 

 (C-Bands) 



G-Bands 

 (R-Bands, 

 Q-Bands) 



Telomere 



^8000-Fold Expansion 



I ■ I 



44+- 



■++ 



Long Tandem 



Repeats 



(Satellite 



Repetitive 



Sequences) 



Interspersed Repeats 



Long 



Interspersed 



Repeats 



LI 



(+ Others) 



Short 

 Interspersed 



Repeats 



Alu Repeats 



Midi- and 



Mini- 

 Satellites 



Telomeric 

 Repeats 



Physical Mapping 



Organization of human chromosomes. This illustration summarizes the major types of sequences and regions that have 

 been characterized on a human genome — or mammalian genome, in general. (Figure provided by C. E. Hildebrand, Los 

 Alamos National Laboratory.) 



43 



