any of the rod-shaped or threadlike DNA-containing structures of cellular organisms that are located in the nucleus of eukaryotes, are usually ring-shaped in prokaryotes (such as bacteria), and contain all or most of the genes of the organism, in animal cells, a structure in the nucleus containing a linear thread of DNA, which transmits genetic information and is associated with RNA and histones, pärilikkustegureid (geene) sisaldavad, DNA-molekulist ja sinna seotud valkudest (kõigepealt histonitest) koosnevad tuumaosad, mis raku jagunemisfaasis on keerdunud kepitaolisteks tihedateks osadeks, niitjas nukleoproteiidne moodustis päristuumsete organismide rakutuumas; on geenide materiaalne kandja; kromosoomide arv on igal looma- v taimeliigil konstantne