Abstract
Mutations at three second-chromosomal loci of Drosophila melanogaster have been isolated, mapped, and shown to be purine nucleoside auxotrophs. Two of the loci, adenosine2 and adenosine3, located at map positions 18.4 and 20, respectively, produce mutations which are supplementable with adenine, adenosine, and inosine. Guanosine supplements mutations at the burgundy locus (55.7); this locus was described previously through a pteridine eye-color defect but identified as an auxotrophic locus after the isolation of a new allele, burgua2-1. The mutation ade2-1 also has defective pteridine metabolism.
