Geni za ribosomnu RNK skupljeni su na kratkim kracima hromosoma13, 14, 15, 20 i 21. Za gen RNR5 postoji u više kopija na hromosomu 22. Svaki klaster gena sadrži 30-40 kopija i kodira 45S RNK proizvod koji se zatim cijepa da formira podjedinice 18S, 5.8S i 28S rRNK. Općenito, geni za RNK ostaju slabo označeni u većini velikih javnih baza podataka.
Najbirnije regije za formiranje i organizaciju jedarceta nalaze se na kratkim (p) kracima hromosoma 1314, 15, 21 i 22.
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