DISTRIBUTION AND LINKAGE OF REPETITIVE CLUSTERS FROM THE HETEROCHROMATIC REGION OF HUMAN-CHROMOSOME-22

The pericentric regions of eukaryotic chromosomes consist of several t ypes of repetitive DNA families. In human chromosome 22, the organizat ion of such families was studied in more detail. In addition to the kn own families of alpha and beta repeats, an additional repeat with a 48 -bp motif was previously assigned to 22pter-q11. Here, we report in mo re detail the distribution of these repeat families, applying pulsed-f ield gel electrophoresis, fluorescence in situ hybridization and physi cal linkage on cosmid recombinants. At least two clusters of 48-bp rep eats are localized on chromosome 22, one on the distal p-arm and one i n the region 22cen-q11. Cosmids from a chromosome 22 library, containi ng both 48-bp and beta-repeats, link both arrays on 22p and define the ir maximum distances to less than 44 kb. Loss of 48-bp repeat sequence s in a Di-George cell line carrying a deletion in 22q11 suggests the p resence of a second cluster in 22q11, a distribution supported by (flu orescene insitu hybridization)FISH signal analysis. As additional memb ers of the 48-bp repeat family can be found on all acrocentric chromos omes it remains to be determined whether the distribution seen on chro mosome 22 is also common in other human acrocentric chromosomes.