Question

Human mitochondrial DNA encodes all of the following EXCEPT __________?

1) RNA polymerase
2) proteins essential to the oxidative respiration functions of the mitochondria
3) ribosomal RNAs
4) transfer RNAs

Answer 1

Human mitochondrial DNA does not encode RNA polymerase; this enzyme is encoded by nuclear DNA. Mitochondrial DNA does encode certain proteins essential for oxidative respiration, ribosomal RNAs, and transfer RNAs.

Step-by-step explanation:

Human mitochondrial DNA encodes all of the following EXCEPT RNA polymerase. The mitochondrion, often referred to as the "powerhouse" or "energy factory" of a cell, contains its own genome and translational machinery, allowing it to transcribe RNAs and translate proteins that are essential to the oxidative respiration functions of the mitochondria, such as mitochondrial ATP synthase. Mitochondrial DNA also encodes ribosomal RNAs (rRNAs) and transfer RNAs (tRNAs), but not RNA polymerase, which is instead encoded by nuclear genes.

Multiple forms of RNA polymerase are found in eukaryotes, with RNA polymerase III being responsible for transcribing tRNAs and some rRNAs. The RNA pol I, RNA pol II, and RNA pol III are all involved in transcription of different types of RNA in the nucleolus and nucleus.

Another crucial role of mitochondria is the import of proteins encoded by the nucleus. These proteins enter the mitochondrial matrix where they contribute to its function, including some that are part of the oxidative phosphorylation pathway.