Polychaos dubium potentially has the largest genome of any existing Earth organism.

Polychaos dubium has one of the largest genomes known for any organism, consisting of 670 billion base pairs or 670 Gbp, which is over 200 times larger than the human genome (3.2 Gbp). The authors of one 2004 study, however, suggest treating that measurement with caution, because it was taken before the advent of modern genomic methods

Source: Polychaos dubium

Despite the suggestion to take the measurement with a grain of salt, we see that other organisms also have relatively large genomes. For instance, the Japanese flower Paris japonica.

Paris japonica has the largest genome of any plant yet assayed, about 150 billion base pairs long. An octoploid and suspected allopolyploid hybrid of four species, it has 40 chromosomes. With 150 billion base pairs of DNA per cell (50 times larger than that of a human haploid genome), Paris japonica may possess the largest known genome of any living organism; the DNA from a single cell stretched out end-to-end would be longer than 300 feet (91 m).

Source: Paris japonica

The fact that DNA has the potential to be so long suggests that it probably also takes up a lot of space (at least on a microscopic scale). Which brings me to my questions:

  1. Just how long can a strand of DNA be (in terms of base pairs) without requiring size accommodations from the nucleus or the cell itself?
  2. What is the largest strand of DNA that can fit inside of a virus?
  3. Is there any limit to how large a genome can be (e.g.: size, weight) in a cell or in a virus?
  4. What kind of biological traits might result in an organism developing a relatively excessively large genome? By extension, might an organism with many different protocols for how to function under different circumstances have a particularly large genome?

Feel free to share any other relevant information as well.


closed as off-topic by Brythan, Xandar The Zenon, Frostfyre, Thucydides, SRM Jan 2 '17 at 16:05

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  • $\begingroup$ define "size accomodations". There already isn't that much space in an ordinary cell nucleus $\endgroup$ – John Dvorak Dec 31 '16 at 20:23
  • $\begingroup$ Without needing to become larger. $\endgroup$ – Christopher Costello Dec 31 '16 at 20:29
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    $\begingroup$ Even existing cells differ in size. DNA size is one of the reasons eukaryotes switched from circular DNA to linear after all. What is your reference cell? I doubt heavily an ordinary virus could fit the entire human genome... $\endgroup$ – John Dvorak Dec 31 '16 at 20:32
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    $\begingroup$ Now, this is a REALLY cool question, but it seems a tad off-topic here. We do have a Biology Stack Exchange, though, and I'm sure they'd love to dig into this. $\endgroup$ – Papayaman1000 Jan 1 '17 at 17:19

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