<P> Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell; most of the DNA can be found in the cell nucleus and, in plants and algae, also in plastids such as chloroplasts . </P> <P> In humans, the 16,569 base pairs of mitochondrial DNA encode for only 37 genes . Human mitochondrial DNA was the first significant part of the human genome to be sequenced . In most species, including humans, mtDNA is inherited solely from the mother . </P>

An organism's traits that are passed on to its offspring through genetic material are its