Molecular nature of 11 spontaneous de novo mutations in Drosophila melanogaster

To investigate the molecular nature and rate of spontaneous mutation in Dro sophila melanogaster, we screened 887,000 individuals for de novo recessive loss-of-function mutations at eight loci that affect eye color. In total, 28 mutants were found in 16 independent events (13 singletons and three clu sters). The molecular nature of the 13 events was analyzed. Coding exons of the locus were affected by insertions or deletions >100 nucleotides long ( 6 events), short frameshift insertions or deletions (4 events), and replace ment nucleotide substitutions (1 event). In the case of 2 mutant alleles, c oding regions were not affected. Because similar to 70% Of spontaneous de n ovo loss-of-function mutations in Homo sapiens are due to nucleotide substi tutions within coding regions, insertions and deletions appear to play a mu ch larger role in spontaneous mutation in D. melanogaster than in H. sapien s. If so, the per nucleotide mutation rate in D. melanogaster may be lower than in H. sapiens, even if their per locus mutation rates are similar.