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The beginning of the Ars Technica article Gene editing crunches an organism’s genome into single, giant DNA molecule begins:

Complex organisms have complex genomes. While bacteria and archaea keep all of their genes on a single loop of DNA, humans scatter them across 23 large DNA molecules called chromosomes; chromosome counts range from a single chromosome in males of an ant species to more than 400 in a butterfly.

Thanks to @Remi.b for tracking down Lukhtanov (2015) The blue butterfly Polyommatus (Plebicula) atlanticus (Lepidoptera, Lycaenidae) holds the record of the highest number of chromosomes in the non-polyploid eukaryotic organisms.

Does mitosis happen in this species of butterfly cells, and if so, does the process that separates the pairs take place in a similar way mechanically to the way it happens in mammal cells such as the 23 pairs in human cells even though there seems to be almost twenty times the number of individual chromosomes?

Has the mechanics of this process ever been imaged or visualized?

Mitosis Mitosis

above: from here and here.

mitotic spindle

above: " Image of the mitotic spindle in a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in red." from here

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    $\begingroup$ For those who would rightly ask for a reference for the claim that there is a species of butterfly that has more than 400 chromosomes, consider having a look at Lukhtanov (2015). $\endgroup$ – Remi.b Aug 4 '18 at 22:28
  • $\begingroup$ @Remi.b Thank you very much for tracking that down! I've added that back into to the question. $\endgroup$ – uhoh Aug 5 '18 at 5:14
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Mitosis was displayed in a lot of organism, also in organism with a very high number of chromosomes. Here's an example of the analysis made in a fish with an average count of 280 chromosomes. Look at the metaphasis of a cell with higher number of chromosomes (Acipenser transmontanus):

enter image description here

This doesn't mean that every chromosome is equal to others: there're microchromosomes, acrocentric chromosomes, meta, sub-meta.. So, the size required into the nucleus (because where're obviously talking about eukaryotic cells) isn't strictly connected with the chromosomes number.

The answer to your question isn't a clear "yes" : the high number of chromosome in a butterfly is connected with a karyotype instability, where some cells received a wrong number of chromosomes into an alterated mitosis. Actually isn't fully clear why and how these errors come out. Here's something else about butterfly karyotype and phylogeny.

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  • $\begingroup$ Thanks for the explanation, link, and image! I just found and put an additional image in the question, and discovered the word "spindle" that I'd been looking for. Mechanically, if there were 400 pairs of chromosomes, I'm trying to understand if there would also be 400 pairs of spindles as well? $\endgroup$ – uhoh Aug 4 '18 at 9:56

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