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Number of complete chromosome sets in a nucleus: haploid (N), diploid (2N), triploid (3N), tetraploid (4N), and so on.



the number that indicates how many times the set of chromosomes characteristic of the germ cells of a given species is replicated in the cell nucleus. The majority of organisms that reproduce sexually are diploid, that is, each of their somatic cells contains two sets of chromosomes (one for each of the haploid germ cells or gametes). In nature and under artificial conditions, ploidy may change in multiples higher that two (eupioidy); there may also be a loss or gain of individual chromosomes (aneu-ploidy).

Euploid increase of the number of chromosome sets (poly-ploidization) occurs if the chromosomes do not separate during cell division. It may also result from the merging of nuclei containing more than one set of chromosomes. There are two types of polyploidy: autopolyploidy, in which the number of homologous sets of chromosomes is increased, and allopolyploidy, which arises when there is a joining, as a result of hybridization, of the genomes of various species. Nonseparation of genomes can occur only in part of the cells of some tissues (somatic polyploidy, which is characteristic of many multicellular animals and plants). Polyploidization can lead to the formation of new plant species and thus serves as an important factor in their evolution (as well as of unicellular organisms). Its significance for species formation in multicellular animals is apparently limited to par-thenogenetic forms. Aneuploidy leads to serious disruptions of development, which often lead to death of the organism and, therefore, does not play a significant role in evolution. Aneuploid cells are common in malignant tumors.

Methods have been elaborated for artificially altering ploidy. They are used to obtain economically valuable forms of plants and for research purposes (for example, to study the action of genes).

References in periodicals archive ?
that a linear correlation between gene expression and ploidy was rarely
The objectives of this proposal are to develop next-generation technologies that leverage haploids; to characterize the conditions and genes that promote ploidy transitions, especially in the presence of drug, in vitro and in vivo and to analyze their fitness consequences.
In this study, we tested 30 previously developed polymorphic microsatellite loci and selected six of them for their application to ploidy verification of C.
This experiment also indicates that somehow the expanding brain mass is telling the SPG to increase their ploidy, but only as much as necessary to maintain the tight junctions between the SPG.
Cytogenetic abnormalities observed in ALL patients are among the most important independent prognostic variables that predict outcome, (5), (6), (9) ploidy and translocations are correlated with prognosis (10), (11)
Human papillomavirus and DNA ploidy in tonsillar cancer--correlation to prognosis.
In any case, a close inspection of life history traits and ploidy in P.
In patients with endometrial carcinoma who did not receive radiotherapy or chemotherapy before surgery, the presence of decreased levels of Rb2/p130 in tumor cells is associated with a significantly increased risk of recurrence and death of disease, independent of tumor stage and ploidy status.
To examine the ploidy of the cultured somatic donor cells at various passages, chromosome counts were determined at passages 3,6, 9,12 and 15 respectively by using standard protocol (Kubota et al.
DNA ploidy of basal cell carcinoma determined by image cytometry of fresh smears.
The plants were divided into different groups according to ploidy levels and 2 species were compared in the same ploidi level.