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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 ?
This haplo identical bone marrow transplant holds out great hope for patients as it expands the pool of donors with partially-matched bone marrow of family members being used in the transplant greatly improving chances of survival for the patient.
They suggested that an interaction of genes involved in pathways of embryonic development rather than haplo insufficiency of single genes in the so-called critical regions is causing complex malformation syndromes due to cytogenetic microaberrations in the 1q4 region.
Mitochondrial DNA haplo groups in four tribes from Tierra del Fuego-Patagonia: inferences about the peopling of the Americas.
These were crossed as males to a genetic stock of the line Red Russian that was monosomic for chromosome H (Red Russian Haplo H).
Because phylogenetic analyses using DNA sequence data are really estimating the phylogeny of the haplo types and species phylogenies are only inferred from these "gene trees," the timing of branching events using DNA sequence data actually date the times of mutation events creating the haplotypes (Harrison 1991).
But then a doctor at Birmingham Children's Hospital suggested manipulating her father Simon's bone marrow using what is known as the HAPLO technique.
6) Pimenta et al, reported association of a new tumor suppressor gene (HRPT2) mutation with ossifying fibroma and proposed that these tumors could develop as a result of haplo in sufficiency of the particular gene.
Her only hope is the specialist Haplo stem cell treatment at the ld d Child ' world-renowned Children's Hospital near Stuttgart, Germany.
According to the result of haplotype analysis, the haplotypes Haplo 1, Haplo 3, Haplo 7 and Haplo 9 were the four main haplotypes, accounting for almost 90% of haplotypes found in the studied sheep populations, and Haplo 1 (CGAG) accounted for more than 30% (Table 3).