Toward a physical map of Drosophila buzzatii: Use of randomly amplified polymorphic DNA polymorphisms and sequence-tagged site landmarks

We present a physical map based on RAPD polymorphic fragments and sequence- tagged sites (STSs) fur the repleta group species Drosophila buzzatii. One hundred forty-four RAPD markers have been used as probes for in situ hybrid ization to the polytene chromosomes, and positive results allowing the prec ise localization of 108 RAPDs were obtained. Of these, 73 behave as effecti vely unique markers for physical map construction, and in 9 additional case s the probes gave two hybridization signals, each oil a different chromosom e, Most markers (68%) are located on chromosomes 2 and 4, which partially a gree with previous estimates on the distribution of genetic variation over chromosomes. One RAPD maps close to the proximal breakpoint of inversion 2z (3) but is not included within the inverted fragment. However, it was possi ble to conclude fi om tl-iis RAPD that the distal breakpoint of 2z(3) had p reviously been wrongly assigned. A total of 39 cytologically mapped RAPDs w ere converted to STSs and yielded an aggregate sequence of 28,431 bp. Thirt y-six RAPDs (25%) did not produce any detectable hybridization signal, and rye obtained the DNA sequence from thr ee of them. Further prospects toward obtaining a more developed genetic map than the our currently available fo r D. buzzatii ar-e discussed.