Admixture
The “flow” of genes from one population into another. African-Americans are an example of an admixed population, resulting from the flow of European genes into African populations.
Allele
One of two or more alternative forms of a given gene.
Alveolar ridge
The bony ridge of the gumline containing the teeth.
Articulation
Movements of the mouth and airway that produce speech.
Association (genetic)
The nonrandom occurrence of a disease or trait and a particular allele or genotype.
Bifid uvula
The small, cone-shaped tissue in the middle of the soft palate that is split into two parts.
Birth defect
An abnormality of structure, function, or body metabolism which often results in a physical or mental handicap. It may be inherited (genetic) or environmental.
Candidate gene
A gene whose protein product suggests that it could be involved in the etiology of a particular disease or trait.
Case-control study
A study in which people with a disease (cases) are compared to people without the disease (controls) to see if chemical exposures or other factors were different for the two groups.
Caudal
Denoting a position more toward the cauda, or tail, than some specified point of reference, same as inferior.
Chromosomal abnormalities
These can be either structural or numerical. Structural abnormalities include translocations, deletions or insertions, duplica tions, and amplifications. Numerical abnormalities are either a gain or loss of chromosomes.
Chromosome
Microscopic, rod-like structure in the cell's nucleus that carries genetic material. Threadlike structures in the nucleus of a cell, consisting of a highly compacted stretch of DNA with associated proteins, which are sets of linear DNA from which the genes are arranged. They carry all of the instructions for a species. Chromosomes come in pairs. Human beings have, in normal cells, 46 chromosomes, or 23 pairs of chromosomes (22 pairs of autosomes and two sex chromosomes, X and Y). In each pair, one chromosome, containing one copy of each gene, is inherited from the mother and one from the father.
Columella
The central, lower portion of the nose which divides the nostrils into right and left.
Confidence interval (CI)
The range of numerical values in which we can be confident (to a computed probability, such as 90% or 95%) that the population value being estimated will be found. Confidence intervals indicate the strength of evidence; wide CIs indicate less precise estimates of effect. The larger the study's sample size, the larger the number of outcome events and the greater the confidence that the true relative risk re duction is close to the value stated. Thus, the CIs narrow and precision is increased.
Congenital defects
Problems or conditions that are present at birth.
Denasality
The quality of voice that lacks normal nasal resonance for m, n, and ng (“head cold” sound).
Dental arch
The curved structure formed by the teeth in their normal position.
DNA (deoxyribonucleic acid)
The substance of heredity. It is the biochemical molecule of which chromo somes and genes are composed. It is the primary genetic material of all cells that tells the cells what to do and when to do it. It contains all of the information necessary for any organism to develop and function. It is the blueprint for all of the structures and functions of a living being. It holds the coded genetic instructions each person inherits from his or her parents. As a coding sequence, it determines the function of a gene, e.g., the synthesis and amino acid sequence of a protein. It is found in all plant and animal cells and carries the genetic information that cells need to replicate, to produce proteins, and to regulate enzyme production. DNA is a long, two-stranded, intertwined, chain-like molecule held together by weak bonds between base pairs of nucleotides (polysugar and phosphate chemical groups). The chain resembles a ladder twisted into a double helix, spiral shape. The four nucleotides, or chemical building blocks, in DNA contain the following bases: adenine (A), guanine (G), cytosine (C), and thymine (T). In nature, base pairs form only between A and T and between G and C; thus, the base sequence of each single strand can be deduced from that of its partner. Most human DNA is nDNA, which is a huge molecule folded tightly and stored in the nucleus of the cell. mtDNA is a much smaller molecule stored in the mitochondria.
mtDNA
Mitochondrial DNA contain the genes that code for some of the enzymes and some of the necessary molecules needed to make those enzymes of the respiratory chain. Mitochondria are the only part of the body cell with separate and unique DNA. Regardless, most of the mitochondria and the respiratory chain are coded by nDNA. mtDNA is inherited only from the mother.
nDNA
Nuclear DNA. Located in the nucleus of the cell, this DNA contains the blueprints for cells that make up the body.
Ectoderm
From the Greek ektos (outside) + derma (skin). Most dorsal layer of cells of the early embryo, which gives rise to the epidermis, neural tube, neural crest, etc.
Effectiveness
A measure of the benefit resulting from an intervention for a given health problem under usual conditions of clinical care for a particular group; this form of evaluation considers both the efficacy of an intervention and its acceptance by those to whom it is offered, answering the question “Does the practice do more good than harm to people to whom it is offered?”
Efficacy
A measure of the benefit resulting from an intervention for a given health problem under the ideal conditions of an investigation; it answers the question, “Does the practice do more good than harm to people who fully comply with the recommendations?”
Etiologic heterogeneity
The phenomenon by which a certain phenotype (or clinical feature) can be produced by different mechanisms.
Exposure assessment
A process that estimates the amount of a chemical that enters or comes into contact with people. An exposure assessment also describes the length of time and the nature and size of a population exposed to a chemical.
Follow-up
Observation over a period of time of an individual, group, or initially defined population whose relevant characteristics have been assessed in order to observe changes in health status or health-related variables.
Gene
The fundamental unit of heredity, it is a working subunit of DNA. DNA is a substance that tells cells what to do and when to do it. A gene is the position on a chromosome (strand of DNA) where a specific DNA sequence, or allele, resides in the cells and mitochondria. It is a specific, unique stretch of DNA sequence that codes for a single characteristic or component of physical development and function. It contains the code for a specific product, typically a protein such as an enzyme. Examples: ABO blood group gene, Rh blood group gene. The information in genes is passed from parent to child; e.g., a gene might tell some cells to make the hair red or the eyes brown. Changes in the sequence from one allele to another can be transmitted to the next generation.
Genetic marker
A segment of DNA with an identifiable physical location on a chromosome whose inher itance can be followed, often referred to simply as a marker.
Genome scan
Evaluation of linkage using a panel of several hundred polymorphic markers, distributed across the entire genome.
Genotype
Genetic constitution of an individual, often used to refer to the combination of alleles at any given locus.
Hereditary
Transmitted or capable of being transmitted genetically from parent to offspring.
Heredity
The passing of a trait such as color of the eyes from parent to child. A person “inherits” these traits through the genes.
Hypernasality
Speech that sounds overly nasal, as if the person is talking through his or her nose.
Hyponasality
Denasality, a lack of normal nasal resonance during speech.
Intention-to-treat analysis
A method for data analysis in a randomized clinical trial in which individual out comes are analyzed according to the group to which the patient was randomized, even if the patient never received the assigned treatment. By simulating practical experience, it provides a better measure of effectiveness (vs. efficacy).
Linkage
The association of genes or markers that lie near each other on a chromosome. Linked genes or markers tend to be inherited together.
Linkage analysis
A method to identify whether or not alleles from two loci segregate together in families.
Linkage disequilibrium
Nonrandom association of alleles at different loci in a population.
Locus (plural, loci)
The position that a gene occupies on a chromosome or within a segment of DNA.
Lod score (log of the odds of linkage)
A statistical estimate of whether two loci are likely to lie near each other on a chromosome and are therefore likely to be inherited together. A lod score of 3.0 (odds of 1000:1 in favor) or more has been traditionally considered strong evidence in favor of linkage.
Malocclusion
A deviation from normal occlusion, i.e., incorrect positioning of the upper teeth in relation to the lower teeth.
Multidisciplinary team
A group of professionals who work together to plan and carry out treatment for patients with cleft lip, cleft palate, and related disorders. The group usually includes surgeons, dental specialists, speech pathologist, and others who meet regularly to evaluate and discuss the patients under their care.
Nasal emission or nasal escape
An abnormal flow of air through the nose during speech, usually indicative of an incomplete seal between oral and nasal cavities.
Nasal septum
The “wall” that divides the nose into right and left halves. It normally joins the roof of the hard palate like an inverted 7.
Nasopharyngoscope
A lighted telescopic instrument used for examining the passages in the back of the throat, useful in assessing velopharyngeal function.
Nonparametric linkage analysis
A number of statistical methods have been developed that do not require a trait locus model to be specified. The most common approach one will encounter in the literature is the affected sib-pair method. This requires families containing two affected siblings and can be shown to be equivalent to a lod score linkage analysis assuming a completely recessive model for the trait locus.
Occlusion
Relationship between upper and lower teeth when they are in contact, refers to the alignment of teeth as well as the relationship of dental arches.
Odds ratio (synonyms: cross-product ratio, relative odds):
A measure of the degree of association, e.g., the odds of exposure among cases compared with the odds of exposure among controls.
p value (probability value)
The probability that a measure of effect is as extreme as or more extreme than that observed even if no effect exists (i.e., if the null hypothesis is false).
Palatal insufficiency
A lack or shortness of tissue preventing the soft palate from contacting the back of the throat (pharynx).
Polymerase chain reaction (PCR)
A molecular biological technique for making, from a very small amount of DNA, an unlimited number of copies of a specific segment of DNA.
Polymorphism
A common variation in the sequence of DNA among individuals.
Population stratification
The existence of two or more subpopulations within a larger population.
Prevalence
The proportion of persons with a particular disease within a given population at a given time.
Prolabium
The central area of the upper lip beneath the center of the nose (columella) and between the philtral columns.
Randomized controlled trial
Study design where treatments, interventions, or enrollment into different study groups are assigned by random allocation rather than by conscious decisions of clinicians or patients. If the sample size is large enough, this study design avoids problems of bias and confounding variables by assuring that both known and unknown determinants of outcome are evenly distributed between treatment and control groups.
Recall bias
Systematic error due to differences in accuracy or completeness of recall to memory of past events or experiences.
Recurrence risk
Probability that a person expresses a disease given the existence of an affected relative (of a given type). For example, the population lifetime risk of developing psoriasis is approximately 2%, but if one has an affected parent or sibling, the recurrence risk is 20%.
Relative risk (RR)
the ratio of the probability of de veloping, in a specified period of time, an outcome among those receiving the treatment of interest or exposed to a risk factor compared with the probability of developing the outcome if the risk factor or inter vention is not present.
Restriction fragment length polymorphism (RFLP)
Genetic variation at the site where a restriction enzyme cuts a piece of DNA. Such variants affect the size of the resulting fragments.
Risk assessment
A process which estimates the likelihood that people exposed to chemicals have health effects. The four steps of risk assessment are hazard identification (Can this substance damage health?), dose response assessment (What dose causes what effect?), exposure assessment (How and how much do people contact it?), and risk characterization (combining the other three steps to estimate risk).
Risk management
The process of deciding how to reduce or eliminate possible health effects by considering the risk assessment, engineering factors (Can engineering procedures or equipment do the job, for how long, and how well?) and social, economic, and political concerns.
Route of exposure
The way in which a person may contact a chemical substance. For example, drinking (ingestion) and bathing (skin contact) are two different routes of exposure to contaminants that may be found in water.
Short tandem repeat polymorphism (STRP)
DNA sequence variation due to the existence of a variable number of copies of the same base sequence on a chromosome.
Single nucleotide polymorphism (SNP, pronounced “snip”)
These are simply point mutations of a sufficiently high frequency to be useful for linkage and association analyses. The nucleotide-wise mutation rate is approximately 10 exp-6 and randomly occurs within coding or noncoding regions, so that there is approximately one SNP per 1000 base pairs. Because of this density, SNPs are more useful for fine mapping of trait loci known to be within a certain chromosomal region.
Susceptibility locus
Gene which contributes (or is thought to contribute) to the risk of disease but may be neither a necessary nor a sufficient cause of disease.
Transmission-disequilibrium test (TDT)
Tests the transmission ratio of alleles at a marker locus from a heterozygous parent to an affected child. There is distortion of the ratio from the mendelian 50:50 only if the marker locus is linked to the trait locus and exhibits allelic association. If a marker locus is close (tightly linked) to the trait locus, then allelic association may be observed; but association does not automatically imply tight linkage.
Velopharyngeal closure
Closing of the nasal cavity from the oral cavity which directs air used in speech through the mouth rather than the nose. It requires interaction of the muscles in the palate and the back of the throat.
Velopharyngeal incompetence
Inability to achieve adequate velopharyngeal closure despite structures that may appear normal.
Velopharyngeal insufficiency
A structural or functional disorder resulting in the inability to achieve adequate separation of the nasal and oral cavities.