The Drop-Dead Mutant Drosophila carries an … The Drop-Dead Mutant Drosophila carries an X-chromosomal recessive mutation that causes severe behavioral defects and brain degeneration, manifested a few days after emergence of the adult. This mutation causes age related neurodegeneration and locomoter dysfunction and these mutants typically have very abbreviated life spans. Some common effects of this mutation are a slightly bent wing margin, frequent hypertrophy of the abdomen, reduced body size, recessive sterility in homozygous mutant females, and brain lesions. These mutants are used to study Parkinson's Disease in some laboratories. Parkinson's Disease in some laboratories.