monosomy

monosomy /mono·so·my/ (mon´o-so″me) existence in a cell of only one instead of the normal diploid pair of a particular chromosome.monoso´mic

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monosomy

[mon′əsō′mē]

Etymology: Gk, monos + soma, body

a chromosomal aberration characterized by the absence of one chromosome from the normal diploid complement. In humans the monosomic cell contains 45 chromosomes and is designated 2n N 1, such as occurs in the XO condition in Turner's syndrome. Compare trisomy. See also aneuploidy. monosomic, adj.

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monosomy [mon″o-so´me]

existence in a cell of only one instead of the normal diploid pair of a particular chromosome, seen in Turner's syndrome,monosomy 9p⁻ disease, and various other conditions. adj., adj monoso´mic.

monosomy 9p⁻ syndrome a rare chromosomal disorder in which a piece of the short arm of the ninth chromosome is broken and often lost. Symptoms include mental retardation, a triangular head with forward angulation of the frontal bone, and various other physical deformities. A support group for more information on this syndrome can be reached at 43304 Kipton Nickel Plate Road, La Grange, OH 44050.

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monosomy

existence in a cell of only one instead of the normal diploid pair of a particular chromosome.

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chromosome 

One of the thread-like structures located within the cell nucleus composed of an extremely long, double-stranded DNA (deoxyribonucleic acid) helix tightly folded around proteins called histones. Each chromosome carries genes that contain the hereditary material that controls the growth and characteristics of the body. There are 46 chromosomes in each human somatic cell organized in 23 pairs, of which 22 pairs are similar in appearance but differ at the molecular level. They are called autosomal chromosomes or autosomes and are designated by a number (with chromosome 1 being the longest, followed by chromosome 2, etc.). The other pair, the sex chromosomes determines the sex of the individual. In mammals the two sex chromosomes of females are alike (homologous) and are referred to as X chromosomes. Males carry one X chromosome along with a much shorter chromosome, the Y chromosome. Each chromosome has a centromere that divides it into two arms, the short arm 'p' and the long arm 'q'. Disorders of chromosome number in which the number of chromosomes is above or below the normal (46) are called aneuploidy. Common forms of aneuploidy are trisomy in which there is one extra chromosome and monosomy in which there is one less, than the normal 46. They rarely cause specific eye diseases but affected individuals present ocular manifestations. Examples: Down's syndrome (trisomy of chromosome 21), Edwards' syndrome (trisomy 18), Turner's syndrome (monosomy 45 XO). There are other chromosome abnormalities such as translocation (one segment of a chromosome is transferred to another chromosome) as may occur in congenital anterior polar cataract, deletion (a loss of a piece of chromosome) as in aniridia, choroideremia, retinoblastoma, etc. Other cases involve damage of a chromosome (e.g. fragile X syndrome). See defective colour vision; gene; mitosis; mutation.

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monosomy

Genetics A type of aneuploidy defined by the formula 2n – 1, where n is the haploid number–eg, Turner syndrome or monosomy X. See Aneuploidy.