Final answer:
Nucleosomes must be repositioned or temporarily disassembled for DNA replication to occur in eukaryotic cells, which is facilitated by chromatin remodeling complexes and influenced by epigenetic modifications like methylation.
Step-by-step explanation:
Impact of Nucleosomes on Eukaryotic DNA Replication
Nucleosomes, which consist of DNA wrapped around histone proteins, play a critical role in the regulation of eukaryotic DNA replication. For replication to commence, the nucleosomes must be temporarily disassembled to allow replication machinery access to the DNA. This is achieved by chromatin remodeling complexes that move, slide, or reposition nucleosomes using energy derived from ATP hydrolysis. Additionally, epigenetic mechanisms such as methylation can also mark the DNA, affecting nucleosome positioning and potentially leading to conditions like cancer when these processes are mutated. Thus, nucleosome arrangement and modification are essential for proper initiation and progression of DNA replication.
DNA at the origin of replication becomes accessible when the pre-replication complex unwinds the DNA helix and proteins like helicase are recruited to open up the DNA. Chromatin modifications allow DNA to slide off proteins, making it available as a replication template. These modifications and the subsequent reassembly of nucleosomes after replication are crucial to regulating the replication process and ensuring accuracy.