A little late with this one, we know (been out of town on spring break!), but Giuseppe Attardi, a pioneering geneticist from Caltech, died in his Altadena home on April 5.  He was 84.   PSN says:

He identified all the genes of the DNA in human mitochondria – often called the powerhouses of biological cells. He then developed techniques for investigating genetic diseases, including Alzheimer’s, and aging in general, which he discovered is associated with changes in mitochondrial DNA (mtDNA).

PSN’s obit is here.