Genetic and Medical Glossary

Glossary

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There are 78 names in this directory beginning with the letter C.
C
the abbreviation for cytosine, a pyrimidine nitrogenous base found in the structure of both DNA and RNA

Café–au–lait spots
any of the medium brown spots usually found on the trunk, pelvis, and creases of the elbow

Campomelic dysplasia
syndrome featuring angulation of the long bones such as femur and tibiae

Camptodactyly
inability of the DIP joints and/or PIP joints of the fingers to be extended 180° by either active or passive means

Candidate gene
a gene suspected of causing a specific disease

Cardiomyopathy
chronic disease of the heart muscle

Carrier
a healthy individual who has one normal allele and one defective allele for a recessive genetic disease

Carrier screening
specialized testing to see whether an individual carries a mutated gene for a specific condition

Carrier testing
testing of an individual who is at risk due to a family history to determine if he or she is a carrier of a mutated or faulty gene for a particular genetic condition

Cat eye syndrome (tetrasomy 22 cen-q11)
chromosomal disorder in which the short arm and a small region of the long arm of chromosome 22 are duplicated four times; characterized by distinctive eye (ocular) abnormality that is sometimes present whereby there is partial absence of ocular tissue (coloboma), often affecting both eyes (bilateral); other symptoms include mild growth delays before birth, mild intellectual impairment, malformations of the skull and facial (craniofacial) region, the heart, the kidneys, and/or anal region; down-slanting eyelid folds (palpebral fissures), widely spaced eyes (ocular hypertelorism), misshapen ears with abnormal outgrowths of skin and small depressions in front of the outer ears (preauricular tags and pits), and/or absence (atresia) of the anal canal, with an abnormal passage (fistula) from the end portion of the large intestine (rectum) into abnormal locations

Caudal
at or near the tail or the posterior part of the body

Cebocephaly
obsolete, nonspecific term for a craniofacial malformation that has morphologic features of a monkey

Centromere
constricted part (central region of the chromosome that separates it into its two arms (the p arm and q arm)

Cerebellar vermis
structure of the brain located in the medial, cortico-nuclear zone of the cerebellum

Cerebellum
part of the brain at the back of the skull whose function is to coordinate and regulate muscular activity

Cerebral cortex
surface layer of gray tissue of the cerebrum, frequently called the gray matter

Cerebral dysgenesis
abnormal brain development in which the brain did not fully develop, grew abnormally, experienced incomplete division, or developed with incomplete organization

Charcot-Marie-Tooth disease type 1A
slowly progressive demyelinating peripheral neuropathy characterized by distal muscle weakness and atrophy, sensory loss, and slow nerve conduction velocity; often associated with pes cavus foot deformity and bilateral foot drop; caused by duplication of PMP22 located on chromosome 17 at 17p12

CHARGE syndrome
multisystem disorder caused by mutation or deletion of the CHD7 gene located at 8q12 on chromosome 8 and characterized by the presence of colobomas and cranial nerve defects (C) heart defects, especially tetralogy of Fallot (H), atresia of the choanae (blocked nasal breathing passages (A), retardation of growth and development (R), genital underdevelopment (G), and ear abnormalities and sensori-neural hearing loss (E)

Cheekbone underdevelopment
reduction in size of the zygomatic process of the temporal bone of the skull, which forms the middle and lateral inferior orbital margin; flat cheekbone, zygomatic underdevelopment

Chiari I malformation
occurs when part of the cerebellum is located below the foramen magnum; may develop when the bony space is smaller than normal, causing the cerebellum and brain stem to be pushed downward into the foramen magnum and into the upper spinal cana

Choanal atresia
narrowing or blockage of the nasal airway by tissue

Chondrodysplasia punctata
disorder of cartilage and bone development that occurs almost exclusively in males; abnormality that appears on x-rays as spots (stippling) near the ends of bones and in cartilage)

Chorio-retinopathy
noninflammatory abnormality of the choroid with extension to the retina

Chorionic villus sampling
a procedure in which fetal cells are obtained from an embryonic structure called the chorion and analyzed for the presence of genetic abnormalities in the fetus

Choroid
a thin vascular layer between the sclera and the retina of the eye; supplies blood to the retina and conducts arteries and nerves to other eye structures

Chromatid
either of two threadlike strands into which a chromosome divides longitudinally during cell division; each contains a double helix of DNA

Chromatin
the material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed. It consists of protein, RNA, and DNA

Chromosomal rearrangement
type of chromosome abnormality involving a change in the structure of the native chromosome and encompass several different classes of events: deletions, duplications, inversions; and translocations

Chromosome
the form in which genetic material is found in the nucleus of a cell; composed of a single DNA molecule that is extremely tightly coiled and usually visible only during the processes of mitosis and meiosis

Chromosome breakpoints
locations on a chromosome where DNA might get deleted, inverted, or swapped around

Chromosome map
a diagram showing the locations of genes on a particular chromosome; generated through analysis of linkage experiments involving those genes

Chromosome mutation
a change in chromosome structure caused by chromosome breakage followed by improper rejoining (eg, deletions, insertions, inversions, and translocations)

Chromosome recombination
process or act of exchanges of genes between chromosomes, resulting in a different genetic combination and ultimately to the formation of unique gametes with chromosomes that are different from those in parents

Cleft lip
fissure in the upper lip that is due to failure of the left and right sides of the fetal lip tissue to fuse; correctable by surgery

Cleido–cranial dysplasia
condition that primarily affects the development of the bones and teeth, resulting in underdeveloped or absent collarbones, delayed closing of the spaces between the bones of the skull, decreased bone density, delayed loss of the primary and delayed appearance of the secondary teeth, unusually shaped, peg-like teeth and misalignment of the teeth and jaws (malocclusion)

Clinical trial
an experimental research study used to determine the safety and effectiveness of a medical treatment or drug

Clone
a molecule, cell, or organism that is an exact genetic copy of another

Cloning vector
a DNA molecule that can be used to transport genes of interest into cells, where these genes can then be copied

Cloverleaf skull
trilobar skull configuration when viewed from the front or behind

Club foot
congenital deformity of the ankles and/or feet in which the foot is turned inward and downward (talipes equinovarus), is angled at the heel with the toes pointing upward and outward (calcaneal valgus), or the front of the foot is turned inward (metatarsus varus)

Clubbing
broadening of the soft tissues of the digital tips in all dimensions associated with an increased longitudinal and lateral curvature of the nails

Clynodactyly
bend or curvature of the fifth fingers (“pinkies") toward the adjacent fourth fingers

Coarctation of the aorta
congenital constriction (narrowing) of the aorta that impedes the flow of blood below the level of the constriction and increases blood pressure

Cockayne syndrome
inherited form of dwarfism caused by a defect in one of the genes involved in the normal repair of DNA (ERCC8 gene for CS-type I mapped to chromosome 5 and ERCC6 gene for CS-type mapped to chromosome 10 at locus 10q11); diagnosed by the presence of three signs: growth retardation (short stature), abnormal sensitivity to light (photosensitivity), and prematurely aged appearance (progeria)

Coding region
portion of a gene's DNA or RNA (exons) that codes for protein. The region is bounded nearer the 5' end by a start codon and nearer the 3' end with a stop codon

Codon
a group of three nucleotides in messenger RNA (mRNA) that represent a single amino acid in the genetic code

Coloboma
hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc

Comparative genomic hybridization
technology wherein a DNA test sample is competitively hybridized with a reference sample of DNA of known sequence to a DNA microarray, used to detect copy number changes in the test sample

Complementary base pairing
hydrogen bond formation in DNA and RNA that occurs only between cytosine and guanine (in both DNA and RNA) or between adenine and thymine (in DNA) or adenine and uracil (in RNA)

Confined placental mosaicism
mosaicism that is seen only in the placenta but not in the fetus

Congenital
present at birth, not necessarily inherited

Congenital defect
a defect or disorder that occurs during prenatal development

Conotruncal heart
general term for truncus arteriosus, transposition of the great arteries, double outlet of the right ventricle, and tetralogy of Fallot; in truncus arteriosus there is a single outflow tract instead of a separate aorta and pulmonary artery

Consanguine
of the same blood or origin; in genetics, the term implies the sharing of genetic traits or characteristics from the same ancestors (eg, cousins)

Contig
A map that shows regions on a chromosome where neighboring portions of DNA overlap; the map provides information about a large segment of a genome by looking at a series of overlapping clones

Contracture
shortening and hardening of muscles, tendons, or other tissue, often leading to deformity and rigidity of joints

Copy number variants
structural chromosomal aberrations - duplications or deletions of relatively small areas of DNA. CNV are present in virtually all individuals. Most CNV do not cause any hereditary disorders but may affect a person's susceptibility to non-hereditary diseases or influence a person's response to some environmental factors

Cor triatriatum
congenital heart defect in which there is a small extra chamber which results in slowing of the passage of blood from the lungs into the heart (left atrium and ventricle) due to the pulmonary veins (returning blood from the lungs) draining into this extra "third atrium"

Corectopia
pupil of the eye is off-center

Cornelia de Lange syndrome
inherited as an autosomal dominant condition involving the NIPBL gene on chromosome 5 or as an X-linked condition involving the SMC1L1 gene on the X chromosome; characterized by delays in physical development before and after birth, characteristic abnormalities of the head and facial (craniofacial) area, malformations of the hands and arms (upper limbs); and mild to severe intellectual impairment; other symptoms include an unusually small, short head (microbrachycephaly), an abnormally long vertical groove between the upper lip and nose (philtrum), a depressed nasal bridge, upturned nostrils (anteverted nares) and a protruding upper jaw (maxillary prognathism)

Costo-vertebral dysplasia
genetic disorder characterized by spinal column abnormalities, dwarfism and a swollen abdomen; also called Jarcho-Levin syndrome

Cowden syndrome
disorder characterized by multiple noncancerous, tumor-like growths called hamartomas and an increased risk of developing certain cancers

Coxa valga
broadening of the head and neck of the femur

Craniofacial
relating to the cranium and the face

Craniosynostosis
a congenital defect involving the skull bones of a newborn, whereby the bones are fused together at birth and require surgical intervention to allow for normal brain development

Cri-du-chat syndrome
also called 5p minus syndrome or “Cat Cry” or syndrome due to the cat-like cry typical of newborns; chromosomal disorder in which a variable portion of the short arm of chromosome 5 is missing or deleted; most deletions are de nova or sporadic; common symptoms include a distinctive cry that resembles a cat’s mewing sound, characteristic facial features, slow growth, and microcephaly; affected children also exhibit delays in the acquisition of skills requiring the coordination of muscular and mental activities (psychomotor disability) and moderate to severe intellectual disability

Critical region
specific portion of a chromosome or a gene that, when altered in some way (deleted, duplicated, or otherwise mutated), produces a characteristic set of phenotypic abnormalities associated with a particular syndrome or disorder

Cryptophtalmos
absent palpebral fissures, with skin passing continuously from the forehead or eyebrow onto the cheek, often with the presence of a tuft of hair; typically associated with a rudimentary or small globe (hidden eye)

Cryptorchidism
absence of one or both testes from the scrotum

CT scan
computerized tomography that combines a series of X-ray views taken from many different angles with computer processing to create cross-sectional images of the bones and soft tissues

Cutaneous
relating to, or affecting the skin

Cutis marmorata
pink marble-like mottling of the skin caused by exposure to cold temperature or associated with various debilitating diseases

Cyclopia
congenital defect characterized by fusion of the orbits into a single cavity containing one eye

Cysterna magna
one of three principal openings in the subarachnoid space between the arachnoid and pia mater layers of the meninges surrounding the brain

Cystic (renal) dysplasia
abnormal tissue development in the kidney that can be confined to a small portion of one (unilateral or both (bilateral) kidneys arranged in a specific pattern within the kidney or randomly present throughout one or both kidneys

Cytogenetics
the study of chromosome number and structure, including identification of abnormalities

Cytosine (C)
a pyrimidine nitrogenous base found in the structure of both DNA and RNA

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