Where does replication occur in eukaryotic cells?

• A. In the nucleus
• B. In the mitochondria
• C. In the cytoplasm
• D. In the ribosomes

Answer: (A)

Replication takes place in the nucleus. In eukaryotic cells, the DNA that must be copied before cell division resides in the nucleus, which is enclosed by a nuclear envelope that keeps the DNA organized and separated from the cytoplasm. During S phase, enzymes like helicase unwind the DNA, primase lays down RNA primers, DNA polymerases synthesize new strands, and ligase seals any gaps, all within the nuclear environment on the chromosomes. While mitochondria do replicate their own circular genomes inside the organelle, the replication of the main nuclear genome occurs in the nucleus, making it the correct site for DNA replication in eukaryotic cells.