P{5'wHy} represents a transgene generated in vivo from P{wHy} as part of a deletion-generation system. In the presence of a source of hobo\T transposase, local transposition of the hobo element in P{wHy}, followed by recombination between the original and newly inserted hobo elements, results in efficient generation of deletions with one endpoint at the site of the original P{wHy} insertion. P{5'wHy} represents the case where the element produced during the recombination event lacks the P-element 3' end of P{wHy} and where the y^+t7.7 marker has been disrupted so that it is no longer functional.