| CH | case history; Chediak-Higashi [syndrome]; chiasma; Chinese hamster; chloral hydrate; cholesterol; Ch... |
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| Ch | chest; Chido [antibody]; chief; child; choline; Christchurch [syndrome]; chromosome |
| CHC | chromosome condensation; community health center; community health computing; community health counc... |
| chr | chromosome; chronic |
| CMGT | chromosome-mediated gene transfer |
| chromosome 8 | Trisomy 8 mosaicism, one of the major cytogenetic syndromes, is characterised by a very suggestive facial dysmorphism, as well as osteoarticular anomalies. Craniofacial dysmorphism includes long face, lop-ear deformities, prominent forehead and overhang of lower lip. Osteoarticular anomalies include camptodactyly, brachydactyly or arachnodactyly, clinodactyly, clubfoot and joint contractures leading to permanent deformities. Deep palmar and plantar creases can be noted in young infants. Skeletal malformations are frequent and severe. Inner organ malformations are rare and kidney or congenital heart defect can be observed. Mental deficiency is not very pronounced. 8p monosomy often occurs de novo. Patients present with a small skull with protruding occiput, short nose, small mouth, and a short and wide neck. Cardiac malformations are frequent. The degree of mental retardation is variable. Inverted duplications of chromosome 8p with distal deletion of 8p are reported. Common clinical traits are hypotonia at birth, large mouth with thin upper lip, bulbous and broad nose, malformed ears, hand and feet anomalies and severe mental retardation. 8p trisomy can result from a parental translocation or can occur de novo. Patients have high prominent forehead, everted fleshy lower lip and flexion contractures of the limbs. Cardiac and cerebral malformations can be observed. Mental retardation is considerably more severe than with trisomy 8 mosaicism. Mosaic tetrasomy 8p resulting from an isochromosome 8p was described. The clinical phenotype can overlap in part with those of trisomy 8 or trisomy 8p, but shows distinctive features including agenesis of the corpus callosum, cardiac malformations and minimal facial dysmorphism. 8q2 trisomy usually results from a parental translocation or inversion. The phenotype includes prominent forehead with hypertelorism, very wide bridge of the nose with blunt nasofrontal angle, microretrognathia, detached and poorly folded ears, buccal deformities including bifid tip of the tongue, cleft upper gum, high arched or cleft palate and bifid uvula. Joint contractures are also noted. Cardiac malformations are frequent and severe. Mental retardation is variable. The Langer-Giedion syndrome, characterised by craniofacial dysmorphism and skeletal abnormalities, is caused by a genetic defect in 8q24.1. Among the gene assignments known for chromosome 8 is the gene for glutathione reductase, the deficiency of which causes a variety of haemolytic anaemia. (05 Mar 2000) |
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| chromosome 9 | Trisomy 9 can be homogenous or mosaic. Microcephaly with dolichocephaly, enophthalmy and microretrognathia are present. Characteristic osteoarticular anomalies include dislocation of the hips, knees or elbows, deformities of the spinal cord and rib anomalies. Inner organ malformations involve cardiac, cerebral, renal and occasionally digestive anomalies. The prognosis is most severe. The 9p monosomy syndrome is characterised by trigonocephaly, long upper lip with undefined philtral borders, short nose, anteverted nares, psychomotor retardation, upward slant of palpebral fissures, dolichomesophalangy. Malformations are severe. The majority of the cases occur de novo, or can result from a parental translocation. 9p trisomy was the first partial trisomy identified before the use of banding techniques and is probably one of the most frequently detected. The majority of pure 9p trisomies occur de novo. In 9q trisomy and associated 9p trisomy, malsegregation of a parental rearrangement is always involved. Craniofacial dysmorphism includes brachycephaly, bulbous nose and short upper lip with a very characteristic asymmetric grin when the mouth opens. The knit brows, slanted palpebral fissures and mouth give a particularly distinctive worried look. The palms are long in comparison with the fingers. A single palmar crease is constant. Malformations are rare in cases of pure 9p trisomy but they are numerous and diverse in cases of associated 9p trisomy. Mental retardation is variable. Life expectancy is not impaired. Tetrasomy 9p is remarkable due to the infrequency of autosomal tetrasomies. The phenotype is variable and the facial dysmorphism can resemble that of 9p trisomy. Malformations are severe and numerous. Homogeneous tetrasomies lead to early death. Mosaicism appears to diminish the severity of the outlook. 9q32 trisomy shows dolichocephaly, deep set eyes with short palpebral fissures, large poorly folded ears, beaked nose, marked microretrognathia, long abnormally implanted fingers and toes and severe developmental delay. Inner organ malformations involve the heart. The trisomy results from a tandem duplication arising de novo or from malsegregation of a parental rearrangement. Interstitial deletion 9q22-q32 is reported with multiple congenital anomalies. The phenotype of ring chromosome 9 is variable and the principal features of 9p monosomy can be observed, as well as certain malformations seen in trisomy 9. Some major genes on chromosome 9 are those for the ABO blood group, fibroblast and leukocyte interferons, familial dysautonomia, Friedreich ataxia, nail-patella syndrome and galactose-1-phosphate uridyltransferase, whose deficiency causes galactosaemia. (05 Mar 2000) |
| chromosome aberration | Any deviation from the normal number or morphology of chromosomes; also the phenotypic consequences thereof. (05 Mar 2000) |
| chromosome aberrations | Deviations from the normal number or structure of chromosomes, not necessarily associated with disease. (12 Dec 1998) |
| chromosome abnormalities | Defects in the structure or number of chromosomes resulting in structural aberrations or manifesting as disease. (12 Dec 1998) |
| chromosome band | A region of darker or contrasting staining across the width of a chromosome; the pattern of band's is characteristic for most chromosomes. (05 Mar 2000) |
| chromosome banding | Staining of bands, or chromosome segments, allowing the precise identification of individual chromosomes or parts of chromosomes. Applications include the determination of chromosome rearrangements in malformation syndromes and cancer, the chemistry of chromosome segments, chromosome changes during evolution, and, in conjunction with cell hybridization studies, chromosome mapping. (12 Dec 1998) |
| chromosome breakage | A type of chromosomal aberration which may result from spontaneous or induced breakage. Alkylating agents, various types of irradiation, and chemical mutagens have been found to cause induced chromosomal breakage. Breakage can induce base pair translocations, deletions, or chromatid breakage. (12 Dec 1998) |
| chromosome complement | The whole set of chromosomes for the species. In humans, the chromosome complement (which is also called the karyotype) consists of 46 chromosomes. (12 Dec 1998) |
| chromosome condensation | <cell biology> The tight packing of DNA into chromosomes in metaphase, in preparation for cell division. (18 Nov 1997) |
| chromosome deletion | Actual loss of a portion of the chromosome. (12 Dec 1998) |
| chromosome disorder | An abnormal condition due to an abnormality of the chromosomes. For example, Down syndrome (the genetic abnormality featuring three chromosome 21s, instead of two, also refered to as trisomy 21) is a chromosome disorder. (12 Dec 1998) |
| chromosome fragile sites | Heritable sensitive regions of chromosomes which show up in vitro as non-staining bands. They are associated with chromosome breakage and other aberrations, and, when located on sex chromosomes, they produce phenotypic abnormalities. No abnormal phenotype has been definitely identified with autosomal fragile sites, but some rare autosomal recessive disorders may be due to homozygosity for fragile sites. Fragile sites are designated by the letters "fra" followed by the designation for the specific chromosome and locus. (12 Dec 1998) |
| chromosome map | The chart of the linear array of genes on a chromosome. The Human Genome Project aims to map all of the human chromosomes. (12 Dec 1998) |
| chromosome mapping | The mapping of the relative locations of genes on a chromosome by analysing linkage frequencies (how often different genes are inherited together) and crossover frequencies (how often different combinations of three or more genes are inherited) or recombination frequencies. (09 Oct 1997) |