STRUCTURE OF THE RYE MIDGET CHROMOSOME ANALYZED BY FISH AND C-BANDING

The diminutive ''midget'' chromosome derived from rye (Secale cereale) was analyzed by C-banding and fluorescence in situ hybridization (FIS H) using DNA probe pSau3A9 that is located in the centromeres of cerea l chromosomes. FISH signals were detected at one end and overlapped on e of the two telomeres of the midget, indicating that the midget is a telocentric chromosome. The FISH and C-banding results show that the c entromere of the midget chromosome is smaller than those of normal whe at and rye chromosomes. These results indicate that one of the breakpo ints occurred in the middle of the centromere of rye chromosome 1R dur ing generation of the midget.