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.
Uniparental inheritance
Although most of the eukaryotic sub-cellular parts do not have their own DNA nor are capable of replication independent of the nucleus, there are some exceptions such as mitochondria and chloroplasts. Not only are these organelles capable of independent DNA replication, translation, and transcription, they are commonly known to inherit genes from only one parental type. In the case of mitochondria, maternal inheritance is almost the exclusive form of inheritance. Although, during egg cell fertilization, mitochondria are brought into the fertilized cell both by the egg cell and the sperm, the paternal mitochondria are usually marked with ubiquitin and are later destroyed. Even if they are not destroyed, the DNA's of different mitochondria rarely genetically recombine with one another. Thus, mitochondria in most animals are inherited from the maternal type only.