Genetic and Medical Glossary

stricture or narrowing of a lacrimal duct

brain malformation that occurs during embryonic development of the cerebellum and 4th ventricle and is characterized by underdevelopment (small size and abnormal position) of the cerebellar vermis (the middle part of the cerebellum), cystic enlargement of the 4th ventricle, and enlargement of the base of the skull (posterior fossa)

deletion of genetic material from the long arm of chromosome 18, specifically, the distal section of 18q typically extending to the tip of the long arm of chromosome 18

a type of chromosomal mutation in which a genetic sequence is lost from a chromosome, usually through an error in recombination de nova mutation: new or spontaneous mutation not inherited from either parent

the genetic material found in all cells; DNA consists of nitrogenous bases (adenine, guanine, cytosine, and thymine), sugar (deoxyribose), and phosphate

dermatologic condition in which small papules or disks of increased dermal elastic tissue appear in early life; autosomal dominant inheritance

congenital defect in which the apex of the heart is situated on the right side of the body

chromosomal disorder characterized by heart abnormalities, cleft palate, distinctive facial features, recurrent infections, breathing problems, kidney abnormalities, low calcium levels in the blood, thrombocytopenia, feeding and gastrointestinal problems, or hearing loss; many have delayed growth and speech development, and learning disabilities

birth defect in which there is an abnormal opening in the diaphragm, causing part of the stomach, spleen, liver, and intestines to go up into the chest cavity near the lungs

a chromosome with two centromeres, usually resulting from an error of recombination

narrow segment of significantly reduced circumference of a digit

a cell or organism with two complete sets of chromosomes; humans normally have two sets of 23 chromosomes, making them diploid

a pathological condition of vision in which a single object appears double

a case in which both copies of a chromosome come from a single parent, rather than one being maternal and one being paternal

situated away from the point of attachment or origin or a central point; located away from the center of the body

process of making an identical copy of a section of duplex (double-stranded) DNA, using existing DNA as a template for the synthesis of new DNA strands

elongated head; cephalic index (ratio of head width expressed as a percentage of head length) less than 76%; increased antero-posterior length of the head compared to width

abnormally long large intestine

an allele or a trait that will mask the presence of a recessive allele or trait; requires only one of the genes to be mutated for the child to be affected (50% chance)

The coiled structure of double-stranded DNA in which strands linked by hydrogen bonds form a spiral configuration, with the two strands oriented in opposite

congenital heart disease in which the aorta rises from the right ventricle (the chamber of the heart that pumps blood to the lungs), instead of from the left ventricle (the normal pumping chamber to the body)

a chromosomal disorder caused by an extra copy of chromosome 21; symptoms include intellectual impairment, congenital heart defects, low muscle tone (hypotonia); a tendency to keep the mouth open with protrusion of the tongue, and distinctive facial characteristics including a short, small head (microbrachycephaly), upwardly slanting eyelid folds (palpebral fissures), a depressed nasal bridge, a small nose, and a relatively flat facial profile

intractable (uncontrollable) form of epilepsy characterized by unilateral (one-sided) clonic or tonic clonic (grand mal) seizures that may be prolonged (> 5 minutes) or progress to status epilepticus (>30 minutes); myoclonic seizures, often called myoclonic jerks, are common but not always present; most cases caused by mutations of the SCN1A gene on chromosome 2q24

disorder of eye movement in which the eye is unable to move outward (toward the ear), and in some cases, inward eye movement (toward the nose) is limited

refers to a blockage in the hollow tube that connects the stomach to the rest of the intestine

a type of chromosomal mutation in which a chromosome region is duplicated because of an error in recombination during prophase I of meiosis

the condition of adults of short stature who are less than 50 inches in height

defective development of an organ, especially the gonads

derived from the Greek dys – meaning abnormal, disease, faulty, impaired and morphology - meaning structure or form

difficulty or discomfort in swallowing, as a symptom of disease

difficulty in speaking due to a physical disorder of the mouth, tongue, throat, or vocal cords

abnormal cell or tissue growth or development

alteration in size, shape, and organization of adult cells

inability to perform coordinated movements

movement disorder in which involuntary muscle contractions cause twisting or repetitive movements