UNUSUAL ORGANIZATION OF THE HUMAN T-CELL RECEPTOR BETA-CHAIN GENE-COMPLEX IS LINKED TO RECOMBINATION HOTSPOTS

Two rare Sfi I polymorphisms of 360 kb and 280 kb present within the h uman T-cell antigen receptor beta-chain gene complex were revealed by pulsed-field gel electrophoresis. They represent allelic variants of t he polymorphic 330- and 300-kb Sfi I fragments previously described. T he 360-kb polymorphism results from duplication of the 30-kb DNA fragm ent responsible for the 330/300-kb insertion/ deletion-related polymor phism. The 280-kb polymorphism results from a 20-kb deletion from the 300-kb Sfi I allele. The rare polymorphisms also map on either side of a Sal I site located near a recombination hotspot, suggesting that ge rm-line duplications and deletions arose from nonhomologous crossover events.