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There are many statements to be found on the internet of the sort:

“DNA replication occurs at elongation rates of about 500 nucleotides per second in bacteria and about 50 nucleotides per second in vertebrates.”

However none that I have read attempt to explain this order-of-magnitude difference. Is it known why?

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    $\begingroup$ What research have you done on your own to answer this question? The Biology.SE community has agreed that questions that show little or no prior research effort are off-topic on this site unless you have shown your attempt at an answer. Please edit your question and tell us where you've looked for answers, what you do know about the topic, and where exactly you still have questions. Our goal is not to simply be an answer site, but rather a site that promotes self-learning with some expert help along the way. $\endgroup$
    – MattDMo
    Feb 5, 2021 at 15:03
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    $\begingroup$ I am not sure why this question has been marked as needing detail or clarity. It seems quite clear to me. And as far as research effort, it would help if the poster had given a source and said he had searched the Internet, but if he had done so he would have found that this statement comes up repeatedly but providing reasons is avoided. The observation has been around for years — it's in the 1992 edition of the Biochemistry of the Nucleic Acids. $\endgroup$
    – David
    Feb 5, 2021 at 18:17
  • $\begingroup$ I have now rewritten to provide clarification and focus. I have deleted the remark "Intuitively, I assume it's just the base rate for growth." As I find this meaningless in molecular terms. I think it is a worthwhile question but I doubt if the answer is known. All I have found is vague statements about histones and greater complexity. However, if someone has anything concrete... $\endgroup$
    – David
    Feb 5, 2021 at 18:26
  • $\begingroup$ hah, I just saw your new comment. I hope my answer is not too vague. $\endgroup$
    – pascal
    Feb 5, 2021 at 19:28
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    $\begingroup$ Note that this is misleading in a way because the eukaryotes divide the replication process among numerous forks starting at multiple initiation sites "Drosophila, alias the fruit fly, has ~ 5,000 such sites while mammalian cells have ~20,000. [...] Our typical animal cell has between 20,000 and 60,000 molecules of pol α whereas our regular bacterium, E. coli has 10 to 20 molecules of DNA pol III." $\endgroup$
    – Fizz
    Feb 8, 2021 at 14:36

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The difference in DNA replication rate between prokaryotes and eukaryotes is still under current research, but the basics are understood. It is very much a matter of complexity, as eukaryotes are more complex in many different ways. I found a very useful reference for this and other kinds of related questions. Briefly, some possible reasons:

[...] in eukaryotes, the DNA template is compacted by the way it winds around proteins called histones. [...]

The DNA-sequence is not as easily accessible in eukaryotes, the unwrapping and re-wrapping of the DNA takes some time.

[...] The coordination of the protein complexes required for the steps of replication and the speed at which replication must occur in order for cells to divide are impressive, especially considering that enzymes are also proofreading, which leaves very few errors behind. [...]

This underlines another rather important factor. The speed of the polymerases replicating DNA is very much related to their accuracy.

[...] This proofreading capability comes with some trade-offs: using an error-correcting/more accurate polymerase requires time (the trade-off is speed of replication) [...]

And just for completeness, here is a compete overview of DNA replication in the three big systems.

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    $\begingroup$ Thanks for pointing out my mistake. Have corrected it. Yes, I’ve heard those arguments before, but I’d like to see some hard data. $\endgroup$
    – David
    Feb 5, 2021 at 21:00

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