Deletion of the full-length isoform of tafazzin, as occurs in tafazzin^Δ761 homozygous mutants causes a change in the fatty acid pattern of cardiolipin but not of phosphatidylcholine and phosphatidylethanolamine. The total amount of cardiolipin is reduced by approximately 80% and the main molecular species, dipalmitoleoyl-dilinoleoyl-cardiolipin, is virtually absent. Heterozygous tafazzin^Δ761 mutant flies exhibit a normal cardiolipin profile.

tafazzin^Δ761 mutants have the same lifespan as wild-type. The heart rate of tafazzin^Δ761 pupae and the locomotor activity of tafazzin^Δ761 larvae is normal.

Adult tafazzin^Δ761 flies exhibit moderate signs of motor weakness. Although this weakness is not severe enough to be picked up by casual observation, quantitative assays clearly demonstrate the reduced ability of adult tafazzin^Δ761 flies to climb against gravity and to fly.

Although no alteration of the myofibril structure is observed, tafazzin^Δ761 indirect flight muscles contain many structurally abnormal mitochondria. This abnormality primarily affects the internal cristae membranes, which present as hyperdense stacks that form swirls, curls, or rings, in many cases extending through almost the entire mitochondrial length. Often, these changes are associated with swelling and disruption of the cristae. Abnormal mitochondria are not homogenously distributed throughout the muscle fibers. Instead, they form clusters that coexist with zones of normal mitochondria. The overall abundance of abnormal mitochondria is >10-fold higher in tafazzin^Δ761 mutants than in wild-type.