Most Robertsonian translocations are dicentric, suggesting that the location of 
chromosomal breaks leading to their formation occur in the acrocentric short 
arm. Previous cytogenetic and molecular cytogenetic studies have shown that few 
Robertsonian translocations retain ribosomal genes or beta-satellite DNA. 
Breakpoints in satellite III DNA, specifically between two chromosome 
14-specific subfamilies, pTRS-47 and pTRS-63, have been indicated for most of 
the dicentric 14q21q and 13q14q translocations that have been studied. We have 
analyzed the structure of 36 dicentric translocations, using several repetitive 
DNA probes that localize to the acrocentric short arm. The majority of the 
translocations retained satellite III DNA, while others proved variable in 
structure. Of 10 14q21q translocations analyzed, satellite III DNA was 
undetected in 1; 6 retained one satellite III DNA subfamily, pTRS-47; and 3 
appeared to contain two 14-specific satellite III DNA sub-families, pTRS-47 and 
pTRS-63. In 10/11 translocations involving chromosome 15, the presence of 
satellite III DNA was observed. Our results show that various regions of the 
acrocentric short arm, and, particularly, satellite III DNA sequences, are 
involved in the formation of Robertsonian translocations.