Editing Nucleomorph (section)

==Persistence of nucleomorphs==
There are no recorded instances of vestigial nuclei in any other secondary plastid-containing organisms, yet they have been retained independently in the cryptomonads and chlorarachniophytes. Plastid gene transfer happens frequently in many organisms, and it is unusual that these nucleomorphs have not disappeared entirely. One theory as to why these nucleomorphs have not disappeared as they have in other groups is that [[introns]] present in nucleomorphs are not recognized by host [[spliceosomes]] because they are too small and therefore cannot be cut and later incorporated into host DNA.

Nucleomorphs also often code for many of their own critical functions, like transcription and translation.<ref name=curtis>Curtis, Bruce et al. "[http://www.nature.com/nature/journal/v492/n7427/full/nature11681.html Algal genomes reveal evolutionary mosaicism and the fate of nucleomorphs]." ''Nature'' 492 :59-65</ref> Some say that as long as there exists a gene in the nucleomorph that codes for proteins necessary for the plastid’s functioning that are not produced by the host cell, the nucleomorph will persist.<ref name=archibald1/> The cryptomonad nucleomorph also codes for genes that function in plastid maintenance.<ref name=McFadden/>

In cryptophytes and chlorarachniophytes all DNA transfer between the nucleomorph and host genome seems to have ceased, but the process is still going on in a few dinoflagellates (MGD and TGD).<ref>[https://www.eurekalert.org/news-releases/916636 Organellogenesis still a work in progress in novel dinoflagellates] (2020)</ref>