Explanation

Besides DNA, a mitochondrion has RNA and its ribosomes also. Thus, a complete protein synthesising machinery is present in mitochondria. The ribosomes of mitochondria are small, $i.e.,$ 55-60 S type, with a large subunit of 40 S and a small subunit of 30 S. The large subunit contain 16-17 S and 5S $r$RNA and the small subunit 12-13 S $r$RNA.