Chromosomal Aberration


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Related to Chromosomal Aberration: aneuploidy, gene mutation

Chromosomal Aberration

 

(also called chromosomal mutation), any of a number of structural changes in chromosomes. These changes result from abnormal divisions within the chromosomes, generally accompanied by reunification of the resulting segments in combinations other than those existing in the original chromosomes.

Structural changes may occur within a single chromosome or between homologous and nonhomologous chromosomes. Such changes include the loss (deletion) or gain (duplication) of a segment of the chromosome, or the exchange (translocation) of a segment of the chromosome with another segment. In inversion, a chromosome segment is deleted, turned through 180°C, and reinserted at the same position on the chromosome. Deletion and duplication disrupt the gene balance, thus altering the organism’s characters. Inversions change only the sequence of the genes in the chromosome, whereas in translocations the genes of the shifted segment move to another linkage group. Neither inversions nor translocations disrupt the gene balance or alter the organism’s phenotypic characters.

When meiosis occurs among heterozygotes that contain one normal chromosome and one chromosome with an inversion, it is difficult for these chromosomes to come together, and crossing over between them does not take place or is infrequent. Aneuploid gametes often appear, and consequently heterozygotes are less fertile than homozygotes, in which both chromosomes of a given pair either have an inversion or are normal. Since heterozygotes have chromosomes in which translocation occurs, heterozygotes produce many aneuploid gametes and are consequently less fertile than homozygotes.

Chromosomal aberrations may arise spontaneously, but they are more likely to occur under the influence of physical and chemical factors. Minor deletions and duplications may result from irregular crossing over. Chromosomal aberrations play an important role in the evolution of organisms: duplications are the main cause of increases in the number of genes. Inversions and translocations may result in genetically isolated homozygous individuals that are more fertile than heterozygotes. In all chromosomal aberrations, the gene position effect is sometimes observed, in which a gene shifted to a new site on a chromosome exerts a different effect on the organism’s phenotype.

Chromosomal aberrations have a practical application in that they may be induced in order to change the linkage groups of genes to produce economically valuable characters in organisms.

S. M. GERSHENZON

References in periodicals archive ?
and others involving curcumin, CuroWhite did not induce statistically significant or concentration-related increases in structural chromosomal aberrations in CHO cells in either the definitive (3 h treatment with and without metabolic activation) or the confirmatory (18 h treatment without metabolic activation) assays of the current in vitro mammalian chromosomal aberrations test.
Twenty-eight gastrointestinal anomalies were described in fetuses that had either multiple other anomalies (15 findings, 54%) or chromosomal aberrations (13 findings, 46%).
glabra rhizomes can significantly protect against bleomycin induced (a) chromosomal aberrations, (b) formation of micronuclei, and (c) DNA dsbs in normal human peripheral blood lymphocytes.
Chromosomal aberrations (CA) are one of the important biological consequences of exposure of the target organism to genotoxic agents.
Moreover, this treatment also highly significantly (Pless than 0.01) induced chromosomal aberrations in the bone marrow cells of mice 24 and 48 h after heptaplatin administration but it did not induce significant changes 72 h after the administration of heptaplatin.
Chromosomal aberration is principally due to double strand breakage (DSB).
A total of 300 well spread metaphases per bulb were analyzed for chromosomal aberrations and 3000 cells were scored for mitotic index.
Chromosomal aberrations, micronuclei and nuclear buds induced in human lymphocytes by 2, 4-dichlorophenoxyacetic acid pesticide formulation.
Root tips of Vicia feba for the study of induction of chromosomal aberrations. Mutation Research, 31: 401-412.
Some patients with the chromosomal aberration are entirely normal or only marginally affected.
For example, the extent of gross chromosomal aberration in barley, i.e., polyploidy and aneuploidy, was shown to be positively correlated with increasing time in culture (Ziauddin and Kasha, 1990; Wang et al., 1992).