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Etymology: Gk, chroma + soma, body; L, aberrare, to wander
any change in the structure or number of any of the chromosomes of a given species. In humans, a number of physical disabilities and disorders are directly associated with aberrations of both the autosomes and the sex chromosomes, including Down, Turner's, and Klinefelter's syndromes. The incidence of most chromosomal disorders is significantly higher than that of single-gene disorders. See also trisomy.
An abnormality in chromosomes regarding number (aneuploidy, polyploidy) or chromosomal material (translocation, deletion, duplication).
See also: aberration
emanating from or pertaining to chromosome.
see chromosomal abnormality (below).
abnormal karyotype; abnormalities can be detected before birth by means of amniocentesis, or after birth, but many are probably never observed because they cause death and disposal of the fetus. The abnormalities are either of number, or of composition of the individual chromosomes. Monosomy and trisomy are examples of numerical abnormalities. Translocations are examples of abnormalities of structure where parts of one chromosome have been transferred to another. The cause of these abnormalities is not known. Their importance is that many of them are linked with structural or functional defects of the animal body. The best known ones in veterinary medicine are those that are related to infertility, e.g. translocation 1/29, translocation 27/29.
fetal cells obtained by amniocentesis or lymphocytes from a blood sample can be cultured in the laboratory until they divide. Cell division is arrested in mid-metaphase by the drug Colcemid, a derivative of colchicine. The chromosomes can be stained by one of several techniques that produce a distinct pattern of light and dark bands along the chromosomes, and each chromosome can be recognized by its size and banding pattern. The chromosomal characteristics of an animal are referred to as its karyotype. This also refers to a photomicrograph of a cell nucleus that is cut apart and rearranged so that the individual chromosomes are in order and labeled. The autosomes are numbered roughly in order of decreasing length. The sex chromosomes are labeled X and Y. Karyotyping is useful in determining the presence of chromosome defects.
see banding (2).
in genetics, loss from a chromosome of genetic material.
see inversion (2).
see linkage (2).
see genetic map.
failure of the chromatids or chromosomes to separate (disjoin) during meiosis.
a technique for identification and isolation of contiguous sequences of genomic DNA.
chromosomal X inactivation
only one of a pair of female (X) chromosomes in the one cell is active, the other is inactivated.