| chromosome 19 | The phenotype of 19q trisomy, which is caused by malsegregation from familial translocation, includes microcephaly with brachycephaly, flat face, widely gaping cranial sutures, hypertelorism and palpebral ptosis, fishlike mouth, short neck, small pudgy hands and feet, growth retardation, slight to very severe mental retardation. Duplication of 19p13.1 and part of 19p13.2 is associated with developmental delay, unusual lower facial features including vertical ridging on the chin, extra philtral pillar, midline ridge on the anterior portion of the tongue and congenital heart defect. A placental karyotype of nonmosaic trisomy 19 was described with an abnormal foetus surviving to midtrimester. Gene assignments on chromosome 19 include the gene for myotonic dystrophy at 19q13.3, Lewis and Lutheran blood groups and the chorionic gonadotrophin |
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| chromosome 20 | The phenotype of trisomy 20p, which results from a parental translocation, includes mild to moderate developmental delay, round face with telecanthus, flat nasal bridge and short palpebral fissures but major pre- and postnatal growth development malformations are rare. The phenotype of interstitial 20p deletion is consistent with Alagille syndrome, an autosomal dominant disease with reduced penetrance and variable expressivity, and is defined by bile duct paucity in association with cardiac, skeletal, ocular and facial abnormalities. 20q13 trisomy shows brachycephaly, hypertelorism, ear anomalies, cleft palate, micrognathia, chin dimple, anteverted nares, CNS malformations, heart defects, psychomotor retardation and reduced life expectancy. Ring chromosome 20 presents with absence of major congenital malformations and paucity of dysmorphic features. Patients can show behavioural problems, seizures, mild dysmorphic features and variable degrees of mental retardation. Sipple syndrome, or multiple endocrine neoplasia type 2, is assigned to chromosome 20p. (05 Mar 2000) |
| chromosome 21 | Down syndrome is the most common chromosome disorder seen in live births and is a leading cause of mental retardation. The frequency of the syndrome is estimated at 1 per 700 births and the risk increases exponentially with maternal age. Some of the manifestations are mental retardation, flat facies, oblique palpebral fissures, epicanthic folds, short broad hands, flattened occiput, cardiac abnormalities, hypotonia, Brushfield spots of the iris, abnormal dermatoglyphics, seizures, increased susceptibility to respiratory infections, increased incidence of leukaemia and premature ageing with Alzheimer-like brain degeneration. 92% to 95% of children born with Down syndrome have a free trisomy as a result of maternal nondisjunction (95%) or paternal nondisjunction (5%). Translocations account for the rest of the trisomies with t(14q21q) or t(15q2q) representing 54.2% of the cases, and t(21q21q) or t(21q22q)5 accounting for 40.9% of the cases. There are a few cases involving other chromosomes. In 55% of the cases, translocations involving the D group chromosomes arise de novo and in 45% of cases a parent carries the translocation. When a G group chromosome is involved t(21q21q) occurs 83.3% of the time. In the vast majority of cases t(21qGq) occurs de novo. Partial trisomy or tetrasomy 21 due to duplication of the distal segment 21q22 results in the classical Down phenotype. Partial trisomy of the proximal segment of 21q21 shows a fairly normal phenotype with moderate mental retardation. Monosomy-21 is not compatible with life. Deletions of chromosome 21 are associated with psychomotor and growth retardation, congenital heart disease, holoprosencephaly, microphthalmia, skeletal malformation, genital hypoplasia and other dysmorphisms. Infants with ring chromosome 21 syndrome, a countertype of trisomy-21, show hypotonia, growth retardation, microcephaly and protruding occiput. Other malformations include ocular, cardiac, digestive, urogenital and skeletal malformation. Mental retardation is severe. (05 Mar 2000) |
| chromosome 3p kinase | <enzyme> Located in the small cell lung cancer tumour suppressor gene region; shows extensive homology to mitogen-activated protein kinase-activated protein kinase 2 (mapkap kinase 2); genbank u09578 Registry number: EC 2.7.10.- Synonym: 3pk protein, 3pk gene product (26 Jun 1999) |
| 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) |
| 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) |
Synonyms : P1-Derived Artificial Chromosomes, PAC (Chromosome), PACs (Chromosomes), Artificial Chromosome, P1-Derived, Artificial Chromosomes, P1-Derived, Chromosome, P1-Derived Artificial, Chromosomes, P1-Derived Artificial, P1 Derived Artificial Chromosomes
Synonyms : Chromosomes, Yeast Artificial, YAC (Chromosome), YACs (Chromosomes), Artificial Chromosome, Yeast, Chromosome, Yeast Artificial, Yeast Artificial Chromosome
Synonyms : Bacterial Chromosome, Bacterial Chromosomes, Chromosome, Bacterial
Synonyms : Chromosome, Fungal, Fungal Chromosome, Fungal Chromosomes
Synonyms : Chromosome, Human, Human Chromosome, Human Chromosomes
| Christensen-Krabbe disease |
(Chris
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| chromatotaxis |
(chro
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| Christian's disease |
(Chris
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| chromatotropism |
(chro
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| chromat- |
(chromat(o)-) [Gr. chr[omacr]ma, gen. chr[omacr]matos color] a combining form denoting relationship to (1) color, or (2) chromatin.
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| Chr | chronic leukemia characterized by granular leukocytes |
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| Chr | a nonreversible lung disease that is a combination of emphysema and chronic bronchitis |
| Chr | pyelonephritis that develops slowly and can lead to renal failure if untreated |
| Chr | renal failure that can result from a variety of systemic disorders |
| Chr | in a slowly developing and long lasting manner |
| Chr | in a habitual and long-standing manner |
| Chr | a record or narrative description of past events |
| Chr | record in chronological order |
| Chr | someone who writes chronicles |
| Chr | an accurate timer for recording time |
| Chr | relating to or arranged according to temporal order |
| Chr | age measured by the time (years and months) that something or someone has existed |