Describe the key steps required to isolate a pure sample of mitochondria from fresh mammalian liver tissue using cell fractionation techniques.

Mitochondria are able to transcribe their own genes. Give one structure found within mitochondria that enables transcription to occur, and describe how this structure differs from its equivalent in the nucleus of a eukaryotic cell.

Scientists investigated the effect of thyroid hormone treatment on the molecular composition of hepatic mitochondria. They measured the mass of cytochrome c oxidase (an inner membrane enzyme) and mitochondrial DNA (mtDNA) in isolated mitochondria from thyroid-treated animals, expressing them as a percentage compared to control animals:

Given that the ratio of cytochrome c oxidase mass to mitochondrial DNA mass in the control animals is $8:1$, calculate the ratio of cytochrome c oxidase to mitochondrial DNA in the thyroid-treated animals.