Final answer:
The true statement about the mitochondrial genome is that it mutates faster than nuclear DNA, making it useful for studying evolutionary relationships and maternal genealogy. Human mitochondrial DNA mostly consists of coding DNA, with many copies present in each cell.
Step-by-step explanation:
The mitochondrial genome holds unique characteristics distinct from nuclear DNA. One key statement regarding the mitochondrial genome that is true is that its evolutionary clock "ticks" much faster than nuclear DNA, meaning it mutates at a more rapid rate. This is useful for scientists studying evolutionary relationships and tracing genealogy, as mitochondrial DNA (mtDNA) is maternally inherited without recombination, providing a clearer lineage. Contrary to statement A, the human mitochondrial genome contains a very low percentage of noncoding DNA; it is primarily coding, with only 37 genes. These genes mainly encode proteins for the electron transport chain. The assertion that mitochondrial genes are present at a lower copy number per cell than nuclear DNA is also false. In fact, each human cell contains multiple mitochondrial genomes—typically 5 to 10 copies per mitochondrion, and each cell can have hundreds to thousands of mitochondria.