The bz2-m allele carries a Ds-induced mutation in the Bz2 gene (M. G. Nuffer, MNL 29:59). We have used the Ds element as a tag for the molecular cloning of a DNA fragment from this locus.

Genomic DNA preparations from bz2-m, Bz2 and a stable recessive derivative of bz2-m were compared in Southern experiments, using probes derived from regions of Ac that are represented in many Ds elements. As these probes detect many bands, it was necessary to identify a band segregating with the bz2-m allele. Such a band was found in a BgIII-digest, and the corresponding 4.3 kb fragment was cloned into the lambda vector NM 1151 (B. Klein and K. Murray, J. Mol. Biol. 133:289, 1979).

A proof that the cloned DNA fragment indeed came from the bz2-m locus was obtained using a DNA fragment flanking Ds as a probe in Southern experiments. DNA derived from the wildtype or from revertants of bz2-m to Bz2 showed a band 1.3 kb smaller than the band detected in DNA from the mutant. A band of wildtype size was also seen in two stable recessive derivatives of bz2-m (which may have arisen by imprecise excision of the Ds element). In DNA from the deletion strain an-bz2-6923, no band hybridizing to the probe was detected.

The size difference between the wildtype and the mutant fragment indicated a length of 1.3 kb for the Ds element. A Ds element of this size is the Ds2 insert in the Adh1-2F11 allele. Restriction mapping and sequence analysis confirmed that the Ds insert in bz2-m is identical in sequence to the Ds insert in Adh1-2F11.

Klaus Theres and Peter Starlinger
 
 

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