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 ?
2005) showing elevated genomic damage 3 months after initiation of MPH therapy using three cellular genotoxicity end points--frequency of micronucleus formation, chromosomal aberrations, and sister-chromatid exchanges (SCE).
Cancer risk in humans predicted by increased levels of chromosomal aberrations in lymphocytes: Nordic study group on the health risk of chromosome damage.
Chromosomal aberration is principally due to double strand breakage (DSB).
However, it is worth mentioning that the phytochemicals in these vegetables could significantly suppress cell division in eukaryotic cells, and may induce chromosomal aberrations at higher concentrations.
Whereas, clerodane diterpenoid was found to be comparatively less effective in controlling the chromosomal aberrations compared to phytosterols.
Usually, these regions are affected by chromosomal translocations but inversions can occur as well with structural chromosomal aberrations affecting 12q14-15, being much more frequent than those affecting 6p21.
27%) of chromosomal aberrations was detected in [greater than or equal to] 30 years age group MDS patients compared to [less than or equal to] 29 yr (27.
Fluoxymeste rone was reported to induce chromosomal aberrations (CAs) and sister chromatid exchanges (SCEs) in cultured human peripheral blood lymphocytes and also increase frequencies of micronuclei and SCEs in bone marrow cells of mice.
Chromosomal aberrations and cancer risk: results of a cohort study from Central Europe, Am J Epidemiol 165:36-43.
Inversion of chromosome 11, inv(11)(p15q22), as a recurring chromosomal aberration associated with de novo and secondary myeloid malignancies: identification of a P1 clone spanning the 11q22 breakpoint.
The FDA has requested that POZEN further address the Agency's concern, prior to approval, about the potential implications from one preclinical in vitro chromosomal aberration study (one of four standard genotoxicity assays) in which genotoxicity was seen for the combination of naproxen sodium and sumatriptan, but not with either component alone.
MBR also offers a micro-clastogenicity screen for predicting the regulatory GLP chromosomal aberration assay.