Question

Most mitochondrial genes are encoded by the nuclear genome
True
False

Answer 1

False

It is not the genes but most of the mitochondrial proteins are encoded by the nuclear genome. For example, the human mitochondrial genome (DNA) encodes 22 tRNAS, 2rRNAs and 13 proteins and they function in the mitochondria. These 13 proteins are components of the electron transport system of mitochondria. But that is not enough for the maintenance and functioning of mitochondria. Many proteins like DNA polymerases for replication of mitochondrial DNA, RNA polymerase for transcription of the mtDNA and approximately fifty ribosomal proteins for the assembly of mitochondrial ribosomes, various inititation, elongation and termination factors for the translation of mitochondrial mRNAs, 20 amino acyl tRNA synthetases needed for amino acylation of mitochondrial tRNAs etc are encoded by the nuclear genome. More over the various transporters on the inner and outer mitochondrial membranes that transport molecules from the cytoplasm in to the mitochondrial matrix and enzymes involved in the TCA cycle, fatty acid oxidation and urea cycle are also encoded by the nuclear genome. These protens are synthesized in the cytoplasm of the cell and exported into the mitochondrial matrix. Therefore the mitochondrial genome encodes only a few proteins needed for the maintenence and functioning of mitochondria but most of these are encoded by the nuclear genome.