Chromosomal Aberration

(redirected from Chromosome abnormalities)
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.

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 ?
Whilst there was a clear association with elevated AFP and the neural tube defects data emerged that there was another cohort of AFP results that were in the lower region of the maternal serum AFP values and were identified to be associated with fetal chromosome abnormalities (14,15).
As the data indicates, the frequency of numerical chromosome abnormalities and MN presence in embryos generated from gamma-irradiated male mice for all six weeks postirradiation is significantly higher than that of the control group (p<0.
NIPT is a far superior approach, compared with conventional screening approaches, to screening for fetal trisomies 21, 18, and 13 in women carrying singleton pregnancies who are at an increased risk for fetal chromosome abnormalities.
In essence, the investigators created a model to study human chromosome inactivation, which opens the doors to understanding the pathology and molecular pathways involved in chromosome abnormalities such as Down syndrome.
Chromosome abnormalities found among 34,910 newborn children: results from a 13-year incidence study in Arhus, Denmark.
Women may choose to detect chromosome abnormalities in the fetus.
Identification of translocations, or chromosome abnormalities, in cancers is important to understanding the molecular pathways at work within cancer cells.
2 Parental chromosome abnormalities are reported in 4% of couples with RM but in only 0.
These findings could be caused by chromosome abnormalities, single gene mutations, or teratogenic agents.
Because of the association between chromosome abnormalities and carcinogenesis, a higher probability to develop polyploidies in ovarian surface epithelium in the elderly should have an impact on the clinical field, in specific situations such as:
Possible reasons include chromosome abnormalities, such as a women with Down's syndrome, enzyme deficiencies, where enzymes damage eggs and prevent the production of the hormone oestrogen, and autoimmune diseases, where the body effectively turns on itself.
Signature, set up in 2003 by Lisa G Shaffer, runs diagnostic cytogenetic testing of chromosome abnormalities in individuals with unexplained physical and developmental disabilities.

Full browser ?