chromosomal aberration

chromosomal aberration

[-sō′məl]

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 Kleinfelter's syndromes. The incidence of most chromosomal disorders is significantly higher than that of single-gene disorders. See also trisomy.

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chromosomal

emanating from or pertaining to chromosome.

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chromosomal aberration

see chromosomal abnormality (below).

chromosomal abnormality

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.

chromosomal analysis

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.

chromosomal banding

see banding (2).

chromosomal chimerism

see chimera.

chromosomal crossover

see crossover.

chromosomal deletion

in genetics, loss from a chromosome of genetic material.

chromosomal inversion

see inversion (2).

chromosomal linkage

see linkage (2).

chromosomal mapping

see genetic map.

chromosomal non-disjunction

failure of the chromatids or chromosomes to separate (disjoin) during meiosis.

chromosomal replication

see replication.

chromosomal walking

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.