FISH OF A MAIZE SH2-SELECTED SORGHUM BAC TO CHROMOSOMES OF SORGHUM-BICOLOR

Fluorescence in situ hybridization (FISH) of a 205 kb Sorghum bicolor bacterial artificial chromosome (BAG) containing a sequence complement ary to maize sh2 cDNA produced a large pair of FISH signals at one end of a midsize metacentric chromosome of S. bicolor. Three pairs of sig nals were observed in metaphase spreads of chromosomes of a sorghum pl ant containing an extra copy of one arm of the sorghum chromosome arbi trarily designated with the letter D. Therefore, the sequence cloned i n this BAC must reside in the arm of chromosome D represented by this monotelosome. This demonstrates a novel procedure for physically mappi ng cloned genes or other single-copy sequences by FISH, sh2 in this ca se, by using BACs containing their complementary sequences. The result s reported herein suggest homology, at least in part, between one arm of chromosome D in sorghum and the long arm of chromosome 3 in maize.