Fig. 7.
An altered genetic background (*; see Materials and Methods) reduces the frequency of spontaneous vesicle fusions to control levels in a synaptotagmin mutant.A, Representative traces of evoked EJPs recorded from wild-type and mutant (*,sytAD3/*,sytnull) larvae. B, Mean mEJP frequency ± SEM is plotted for wild-type (black bars; n = 6),*,sytAD3/*,sytnull(hatched bars; n = 4), and*,sytAD3/sytnull(white bars; n = 10) larvae. mEJP frequency was increased significantly as compared with wild-type in*,sytAD3/sytnullmutants (p ≪ 0.001; Student’s ttest), as seen previously in other syt mutations. This increase was suppressed when the portion of the second chromosome denoted * (see Materials and Methods) was made homozygous; mEJP frequency in this mutant (*,sytAD3/*,sytnull) was not significantly different from wild-type larvae (p < 0.8; Student’s ttest).