I am interested in deviations from standard eukaryotic biological mechanisms:

  • Sperm chromatin lacks nucleosomes, and are instead highly condensed by protamines. (most eukaryotic chromatin has chromatin with nucleosomes).
  • Camelid and cartilaginous fish antibodies are single-domain (most vertebrates have heavy chain + light chain antibodies).
  • Drosophila homologous chromosomes undergo transvection and are tightly paired. (Transvection is not usually observed in eukaryotes.)

These are some of the unique peculiarities I've found among model systems that deviate from "expected" biology. Is there a running database that catalogues unique attributes of different model systems? If not for trivia, I find them extremely inspiring for mechanistic studies!

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    $\begingroup$ I find this to be a very interesting question, but I think that it's critically important for you to be clear about 2 things: 1) what is the taxonomic level of focus? 2) for any given taxonomic level, what is the "expected" biology that is deviated from? I have edited to try to reflect this better. $\endgroup$ Commented Apr 27, 2022 at 5:30
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    $\begingroup$ No database that I've heard about. But you can add achiasmy to your list (absence of homologous recombination in some drosophilid and lepidopteran males). I've always found that intriguing and sometimes a useful exploit for genetic crossings. $\endgroup$
    – S Pr
    Commented Apr 27, 2022 at 11:53


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