Polyploidy number

Chromosome The DNA-bearing structure that carries the inheritable characteristics of a given organism. The number of chromosomes is constant for any given species. Chromosomes may be present in the haploid, diploid, or polyploidy number. 

Chinese hamster ovary cells in which there has been an extensive rearrangement of chromosome material and the chromosome number may not be constant from cell to cell, are frequently used. Polyploidy, endoreduplication and high spontaneous chromosome aberration frequencies can sometimes be found in these established cell lines, but careful cell culture techniques should minimize such effects. Cells should be treated in exponential growth when cells are in all stages of the cell cycle. 

Positive results in the mammalian in vivo bone marrow chromosome aberration test indicate that a substance induces stmctural chromosome aberrations in the bone marrow of the species tested. An increase in polyploidy (a multiple of the haploid chromosome number (n) other than the diploid number, i.e., 3n, 4n and so on) may indicate that a substance has the potential to induce numerical aberrations (change in the number of chromosomes from the normal number characteristic of the animals utilized). 

GENOMIC MUTATION A change in the number of chromosomes in the genome that does not alter the structure or arrangement of genes in the chromosomes. (See also ANEUPLOIDY, POLYPLOIDY, CHROMOSOMAL MUTATION, GENE MUTATION, and POINT MUTATION)... 

Polyploidy A condition in which number of chromosomes in a cell(s) is more than normal numbers. 

In addition, the assay can be used for the detection of compounds that induce polyploidies. An increase in the number of polyploidy cells may indicate that a compound has the potential to induce numerical aberrations. 

Aneuploidy/polyploidy—decrease/increase in the number of chromosomes... 

The nucleus of the liver cell has 1 or 2 nucleoli, (s. fig. 2.18) Its proportion of the cell volume is 6%. About 20-25% of liver cells have 2 nuclei, presumably as a sign of increased cell activity. Number, size, nuclear pattern or nuclear changes are very varied due to diverse influences (e.g. age, nutrition, physiological moulting ) - above all in pathological processes. About 10-44% of the nuclei are diploid, 55-80% are tetraploid and 5-6% are octoploid. Increasing polyploidy is deemed a precancerous phase. The nucleus has a bilaminar nuclear membrane (D.W. Fawcett, 1955). The inner nuclear... 

Genome mutations. Genome mutations occur when the total number of chromosomes is altered (aneuploidy) (Russell, 1983). Polyploidy arises when an extra copy of every chromosome is made, and trisomy arises when only one extra copy of a single chromosome is present. If an entire chromosome is absent, the consequent disorder is called a monosomy. 

The answer is e. (Murray, pp 812-828. Scriver, pp 3-45. Sack, pp 57-84. Wilson, pp 123-148.) Aneuploidy involves extra or missing chromosomes that do not arise as increments of the haploid chromosome number n. Polyploidy involves multiples of n, such as triploidy (3n = 69,XXX) or tetraploidy (4n = 92,XXXX). Diploidy (46,XX) and haploidy (23,X) are normal karyotypes in gametes and somatic cells, respectively. A 90,XX karyotype represents tetraploidy with two missing X chromosomes, which has been seen in one patient who had features that resembled those of Turner s syndrome. 

With the exception of natural polyploidy in certain tissues and the absence of nuclei in eiythrocytes, the chromosome complement of the majority of somatic cells in the human body is presumed to be the initial complement—the one present in the zygote. Tissue culture cells derived from normal human donors have, in most cases, the diploid chromosome number. Strains of skin fibroblasts have been available which can be maintained in the diploid state for as long as 2 years, although a gradual decline in growth activity occurs toward the end of this period (Hayflick and Moorhead, 1961 Hayflick, 1965). In addition, cell lines with apparently normal karyotypes have been established from the peripheral leukocytes of normal individuals (Moore et aL, 1967 Glade et aL, 1968 Huang et aL, 1969 Christofinis, 1969). 

Colchicine is used to introduce polyploidy in plants and causes doubling or increase in the chromosome number of... 

The increase in the ploidy level often causes anatomical and structural changes, such as changes in the leaves, cell size, number of chloroplasts in cells, etc. [122, 123]. These effects of polyploidy may influence photosynthesis [124], the enzyme activities, the photosynthetic electron transport, and isoenzyme activity [13]. All these manifestations of polyploidy often lead to gigantism, i.e., to increased accumulation of plant biomass [116] and a change in secondary metabolism [13]. 

Types of aberrations other than translocations are much less frequent. Small fragments are sometimes observed in dividing spermatocytes of mice given X-irradiation, but their incidence is always very low. 46-48) The mean number of X-Y univalents remains unaltered in most animals, although a few individuals can display an increase to as much as 40%. The causes and the meaning of this high incidence are so far unknown, and no relation seems to exist between the type of treatment and the number of animals with a high rate of X-Y univalents. Finally, the incidence of polyploidy seems not to increase after irradiation. 

All species of Larix, like most other genera in the Pinaceae, have a haploid number of 12 chromosomes (Wright, 1962). Polyploidy and aneuploidy are rare in conifers. A cross between L. occidentalis and L. decidua (European larch) produced a single triploid hybrid (Larsen and... 

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