Mitochondrial matrix
The cytosolic, intermembrane space, compartment has a water content of 3.8 μl/mg protein, while the mitochondrial matrix 0.8 μl/mg protein. It is not known how mitochondria maintain osmotic balance across the inner mitochondrial membrane, although the membrane contains aquaporins that are believed to be conduits for regulated water transport. Mitochondrial matrix has a pH of about 7.8. Mitochondrial DNA was discovered by Nash and Margit in 1963. One to many double stranded mainly circular DNA is present in mitochondrial matrix. Mitochondrial DNA is 1% of total DNA of a cell. It is rich in Guanine and Cytosine content. Mitochondria of mammals have 55s ribosomes.
Human mitochondrial genetics
Mitochondrial DNA had traditionally had the two strand of the DNA designated the heavy and the light strand, due to their boyant densities during separation in cesium chloride gradients, which was found to be related to the relative G+T nucleotide content of the strand. However, confusion of labeling of this strands is widespread, and appears to originate with a identification of the majority coding strand as the heavy in one influential article in 1999. In humans, the light strand of mtDNA carries 28 genes and the heavy strand of mtDNA carries only 9 genes. Eight of the 9 genes on the heavy strand code for mitochondrial tRNA molecules. Human mtDNA consists of 16,569 nucleotide pairs. The entire molecule is regulated by only one regulatory region which contains the origins of replication of both heavy and light strands. The entire human mitochondrial DNA molecule has been mapped.