agenesis: Lack of development of something. For example, agenesis of a toe means that toe failed to form.

affected: An individual who manifests symptoms of a particular condition.

allelic: Pertaining to an allele, an alternative form of a gene. A single allele is inherited from each parent.

anecdotal: Based on personal observation, case study reports, or random investigations rather than systematic scientific evaluation: anecdotal evidence.

anomaly: A deviation from the common rule, type, arrangement, or form.

autosomal dominant: Describes a trait or disorder in which the phenotype is expressed in those who have inherited only one copy of a particular gene mutation (heterozygotes); specifically refers to a gene on one of the 22 pairs of autosomes (non-sex chromosomes).

band: When chromosomes at a particular stage in cell division are stained using one of several types of preparations, a specific pattern of light and dark stripes (bands) appear which can aid in identifying the chromosome and evaluating its structure.

brachycephaly: A short head, one that is short in diameter from front to back.

brachydactyly: Short, stubby fingers and toes.

cardiac: Having to do with the heart.

circadian: Refers to events occurring within a 24-hour period, in the span of a full (24-hour) day, as in a circadian rhythm. Circadian rhythmicity is a fundamental property possessed by all organisms. These rhythms are driven by an internal time-keeping system: a clock.

chromosome: Physical structure consisting of a large DNA molecule organized into genes and supported by proteins called chromatin.

cleft palate: An opening in the roof of the mouth (the palate) due to a failure of the palatal shelves to come fully together from either side of the mouth and fuse, as they normally should, during embryonic development.

conductive hearing loss: Hearing loss due to problems with the bones of the middle ear.

congenital: Present from birth, but not necessarily genetic.

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

cytogenetics: The study of the structure, function, and abnormalities of human chromosomes.

deletion: Absence of a segment of DNA; may be as small as a single base or as large as one or more genes.

developmental delay: Behind schedule in reaching milestones of early childhood development.

diagnostic testing: Testing designed to confirm or exclude a known or suspected genetic disorder in a symptomatic individual or, prenatally, in a fetus at risk for a certain genetic condition.

dysmorphology: The clinical study of malformation syndromes.

EEG: Electroencephalogram, technique for studying the electrical current within the brain. Electrodes are attached to the scalp. Wires attach these electrodes to a machine which records the electrical impulses. The results are either printed out or displayed on a computer screen. Electroencephalogram is abbreviated EEG.

exon: Coding sequence of DNA present in mature messenger RNA.

failure to thrive: A description applied to children whose current weight or rate of weight gain is significantly below that of other children of similar age and sex.

familial: A phenotype that occurs in more than one family member; may have genetic or non-genetic etiology.

fine motor skills: Coordination of small muscle movements which occur e.g., in the fingers, usually in coordination with the eyes.

FISH: (synonym: fluorescent in situ hybridization) A technique used to identify the presence of specific chromosomes or chromosomal regions through hybridization (attachment) of fluorescently-labeled DNA probes to denatured chromosomal DNA. Examination under fluorescent lighting detects the presence of the hybridized fluorescent signal (and hence presence of the chromosome material) or absence of the hybridized fluorescent signal (and hence absence of the chromosome material).

gamete: The sperm or the egg. Each human gamete normally has 23 chromosomes, the haploid number of chromosomes, half the number of chromosomes contained in most types of cells in the body.

gene: The basic unit of heredity, consisting of a segment of DNA arranged in a linear manner along a chromosome. A gene codes for a specific protein or segment of protein leading to a particular characteristic or function.

gene product: Genes are transcribed into segments of RNA (ribonucleic acid), which are translated into proteins. Both RNA and proteins are products of the expression of the gene.

genetic counseling: A process, involving an individual or family, comprising: evaluation to confirm, diagnose, or exclude a genetic condition, malformation syndrome, or isolated birth defect; discussion of natural history and the role of heredity; identification of medical management issues; calculation and communication of genetic risks; provision of or referral for psychosocial support.

germline mosaicism: Two or more genetic or cytogenetic cell lines confined to the precursor (germline) cells of the egg or sperm; formerly called gonadal mosaicism.

gross motor skills: The movements of the large muscles of the body.

hypercholesterolemia: High blood cholesterol. This can be sporadic (with no family history) or familial.

hypoplasia: Underdevelopment or incomplete development of a tissue or organ.

hyporeflexia: Underactivity of bodily reflexes.

hypotonia: Decreased tone of skeletal muscles. In a word, floppiness.

immunoglobulin: A protein produced by plasma cells and lymphocytes and characteristic of these types of cells. Immunoglobulins play an essential role in the body's immune system. They attach to foreign substances, such as bacteria, and assist in destroying them. Immunoglobulin is abbreviated Ig. The classes of immunoglobulins are termed immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE).

imprinting: The process by which maternally and paternally derived chromosomes are uniquely chemically modified leading to different expression of a certain gene or genes on those chromosomes depending on their parental origin.

insertion: A chromosome abnormality in which material from one chromosome is inserted into another nonhomologous chromosome; a mutation in which a segment of DNA is inserted into a gene or other segment of DNA, potentially disrupting the coding sequence.

lethargy: 1. Abnormal drowsiness, stupor. 2. A state of indifference.

marker: An identifiable segment of DNA (e.g., RFLP, VNTR, microsatellite) with enough variation between individuals that its inheritance and co-inheritance with alleles of a given gene can be traced; used in linkage analysis.

melatonin: A hormone produced by the pineal gland, melatonin is intimately involved in regulating the sleeping and waking cycles, among other processes.

microdeletion syndrome: (synonym: contiguous gene deletion syndrome) A syndrome caused by a chromosomal deletion spanning several genes that is too small to be detected under the microscope using conventional cytogenetic methods. Depending on the size of the deletion, other techniques, such as FISH or other methods of DNA analysis can sometimes be employed to identify the deletion.

micrognathia: Abnormal smallness of one or both jaws.

missense mutation: A single base pair substitution that results in the translation of a different amino acid at that position.

molecular genetic testing: (synonyms: DNA testing, DNA-based testing, molecular testing) Testing that involves the analysis of DNA, either through linkage analysis, sequencing, or one of several methods of mutation detection.

mosaicism: Within a single individual or tissue, the occurrence of two or more cell lines with different genetic or chromosomal constitutions.

mutation: (synonyms: sequence alteration, splicing mutation) Any alteration in a gene from its natural state; may be disease-causing or a benign, normal variant.

myopia: Nearsightedness, the ability to see close objects more clearly than distant objects.

nocturnal: Of or pertaining to the night.

nucleotide: A molecule consisting of a nitrogenous base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a phosphate group, and a sugar (deoxyribose in DNA; ribose in RNA). DNA and RNA are polymers of many nucleotides.

ocular: Having to do with the eye.

otitis media: Inflammation of the middle ear characterized by the accumulation of fluid in the middle ear, bulging of the eardrum, pain in the ear and, if eardrum is perforated, drainage of purulent material (pus) into the ear canal.

otolaryngology: A medical and surgical specialty concerned with the diagnosis, management, and treatment of diseases and disorders of the ear, nose, throat (ENT) and related structures of the head and neck, including the sinuses, larynx (voice box), oral cavity, and upper pharynx (mouth and throat).

peripheral neuropathy: A problem with the functioning of the nerves outside the spinal cord. Symptoms may include numbness, weakness, burning pain (especially at night), and loss of reflexes.

phenotype: The observable physical and/or biochemical characteristics of the expression of a gene; the clinical presentation of an individual with a particular genotype.

polymorphism: Natural variations in a gene, DNA sequence, protein, or chromosome that have no adverse effect on the individual and occur with fairly high frequency in the general population.

polysomnography: Continuous recording of specific physiologic variables during sleep. polysomnography typically records brain wave changes (electroencephalogram), eye movements (electrooculogram), muscle tone (electromyogram), respiration, electrocardiogram (EKG), and leg movements.

prenatal diagnosis: (synonym: prenatal testing) Testing performed during pregnancy to determine if a fetus is affected with a particular disorder. Chorionic villus sampling (CVS), amniocentesis, periumbilical blood sampling (PUBS), ultrasound, and fetoscopy are examples of procedures used either to obtain a sample for testing or to evaluate fetal anatomy.

proband: (synonyms: index case, propositus) The affected individual through whom a family with a genetic disorder is ascertained; may or may not be the consultand (the individual presenting for genetic counseling).

probe: A specific, pre-fabricated sequence of DNA or RNA, labeled by one of several methods, used to detect the presence of a complimentary sequence by binding (hybridizing) to it.

psychotropic medication: Any medication capable of affecting the mind, emotions, and behavior.

REM sleep: REM sleep is the portion of sleep when there are rapid eye movements (REMs). Dreams occur during REM sleep. We typically have 3 to 5 periods of REM sleep per night. They occur at intervals of 1-2 hours and are quite variable in length. An episode of REM sleep may last 5 minutes or over an hour. About 20% of sleep is REM sleep. If you sleep 7-8 hours a night, perhaps an hour and half of that time, 90 minutes, is REM sleep.

rearrangement: A structural alteration in a chromosome, usually involving breakage and reattachment of a segment of chromosome material, resulting in an abnormal configuration; examples include inversion and translocation.

recombination: (synonym: crossing over) The exchange of a segment of DNA between two homologous chromosomes during meiosis leading to a novel combination of genetic material in the gamete.

recurrence risk: The likelihood that a trait or disorder present in one family member will occur again in other family members in the same or subsequent generations.

renal: Having to do with the kidney.

scoliosis: Sideways (lateral) curving of the spine (the backbone).

screening: Testing designed to identify individuals in a given population who are at higher risk of having or developing a particular disorder, or having a gene mutation for a particular disorder.

sensory integration: A form of occupational therapy in which special exercises are used to strengthen the patient's sense of touch (tactile), sense of balance (vestibular), and sense of where the body and its parts are in space (proprioceptive).

sequence analysis: (synonyms: gene sequencing, sequencing) Process by which the nucleotide sequence is determined for a segment of DNA.

sequence alteration: (synonym: mutation) Any alteration in a gene from its natural state; may be benign (commonly referred to as a "polymorphism"), pathogenic, or of unknown significance.

simplex case: A single occurrence of a disorder in a family.

sleep apnea: The temporary stoppage of breathing during sleep, often resulting in daytime sleepiness.

strabismus: A condition in which the visual axes of the eyes are not parallel and the eyes appear to be looking in different directions. In divergent strabismus, or exotropia, the visual axes diverge. If the visual axes converge, it is called convergent strabismus or esotropia.

taurodontism: A dental condition marked by the enlargement of the pulp cavities and the reduction of the roots.

translocation: (synonym: chromosome rearrangement) A chromosome alteration in which a whole chromosome or segment of a chromosome becomes attached to or interchanged with another whole chromosome or segment, the resulting hybrid segregating together at meiosis; balanced translocations (in which there is no net loss or gain of chromosome material) are usually not associated with phenotypic abnormalities, although gene disruptions at the breakpoints of the translocation can, in some cases, cause adverse effects, including some known genetic disorders; unbalanced translocations (in which there is loss or gain of chromosome material) nearly always yield an abnormal phenotype.

tympanostomy tube: A small plastic tube inserted into the eardrum to keep the middle ear aerated for a prolonged period of time.

velopharyngeal insufficiency:  An anatomical deficiency in the soft palate or superior constrictor muscle resulting in the inability to achieve velopharyngeal closure and often resulting in defective speech.

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