A Patient with a Mitochondrial Disease Is Found to Have

A patient with a mitochondrial disease is found to have a mutation in Gene X. A homologous gene in a Drosophila (fruit fly) , did not cause a similar deficit. What does this suggest?

A) Gene X is highly conserved between humans and Drosophila.
B) Gene X is not conserved between humans and Drosophila.
C) Gene X is encoded in nuclear DNA.
D) Gene X is encoded in mitochondrial DNA.
E) Gene X is a redundant protein in Drosophila.