Final answer:
The component found only in eukaryotic genomes and not in prokaryotic genomes is telomeres, which are protective ends on the linear chromosomes of eukaryotes, not needed in the circular chromosomes of prokaryotes. So, the correct answer is B. telomeres.
Step-by-step explanation:
The component that is found only in eukaryotic genomes and not in prokaryotic genomes is B. telomeres.
Unlike prokaryotes which have a single, circular chromosome, eukaryotes have multiple, linear chromosomes with distinct ends known as telomeres.
These telomeres protect the ends of chromosomes from deterioration or from fusion with neighboring chromosomes.
Prokaryotes do not have this feature because their DNA is circular and thus does not require such protective ends.
Additionally, while both prokaryotic and eukaryotic cells package their DNA, eukaryotes wrap their chromosomes around histone proteins forming structures such as nucleosomes and higher-order chromatin, which is different from the supercoiling found in prokaryotes managed by DNA gyrase.
So, the correct answer is B. telomeres.