P-ELEMENT-MEDIATED IN-VIVO DELETION ANALYSIS OF WHITE-APRICOT - DELETIONS BETWEEN DIRECT REPEATS ARE STRONGLY FAVORED

We have isolated and characterized deletions arising within a P transp oson, P[hsw(a)], in the presence of P transposase. P[hsw(a)] carries w hite-apricot ( w(a)) sequences, including a complete copia element, un der the control of an hsp70 promoter, and resembles the original w(a) allele in eye color phenotype. In the presence of P transposase, P[hsw (a)] shows a high overall rate (approximately 3%) of germline mutation s that result in increased eye pigmentation. Of 234 derivatives of P[h sw(a)] with greatly increased eye pigmentation, at least 205 carried d eletions within copia. Of these, 201 were precise deletions between th e directly repeated 276-nucleotide copia long terminal repeats (LTRs), and four were unique deletions. High rates of transposase-induced pre cise deletion were observed within another P transposon carrying unrel ated 599 nucleotide repeats (yeast 2 mu FLP; recombinase target sites) separated by 5.7 kb. Our observation that P element-mediated deletion formation occurs preferentially between direct repeats suggests gener al methods for controlling deletion formation.