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   A large genetic screen was performed to identify mutants of the fruit fly Drosophila melanogaster that show altered behavior in a gravitaxic maze assay.  For 18 of the mutant lines isolated, it proved possible to identify the affected gene.  A subset of these genes has been chosen for further study.  All novel genes are being named after astronauts to recognize our support from NASA.  We will present our findings to date on the genes john glenn (jog) and alan shepard (alan).   jog encodes a protein indicated  to play a role in receptor tyrosine kinase -related signaling.   Our gravitaxic mutation to the gene specifically interrupts an exon of the gene that is unique to one of the two isoforms of the protein.  We have used the original mutation to the gene to generate further mutations that delete much of this first exon.  These more severe mutations display even greater behavioral abnormalities including in one case a complete failure to traverse the gravitaxic maze.  We hypothesize that the isoform of the protein affected by these mutations is largely dedicated to behavioral responses.  alan encodes a RNA binding protein.  Our gravitaxic mutation of alan also appears to influence a subset of the transcripts of the affected gene.  However, some of the additional mutations to this gene that we have generated show developmental defects particularly in the eyes and head bristles.  We hypothesize that this gene has roles in development as well as behavioral responses.