The Genetic Disorders of Mucociliary Clearance Consortium
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Term Glossary

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A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Allele: One version of a gene at a given location (locus) along a chromosome.

Alveolus (plural alveoli): Thin-walled air sac in the lung which permits gas exchange.

Autosomal: Refers to any of the chromosomes other than the sex-determining chromosomes (i.e., the X and Y) or the genes on these chromosomes.

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).

Autosomal Recessive: Describes a trait or disorder requiring the presence of two copies of a gene mutation at a particular locus in order to express observable phenotype; specifically refers to genes on one of the 22 pairs of autosomes (non-sex chromosomes).

Axoneme: The structure of a cilium.

B

Basal Body: A structure in the cytoplasm that anchors microtubules to the cell.

Base Pair (bp): Two nitrogenous bases (adenine and thymine or guanine and cytosine) held together by weak bonds. Two strands of DNA are held together in the shape of a double helix by the bonds between base pairs.

Base Sequence: The order of nucleotide bases in a DNA molecule.

Base Sequence Analysis: A method, sometimes automated, for determining the base sequence.

Bronchiectasis: abnormal dilation of the airways caused by chronic infection and inflammation.

Bronchiole: the smallest airway in the lung that branches into the alveoli.

Bronchoalveolar Lavage: the collection of lower airway and alveolar secretions using a bronchoscope.

Bronchoscopy: the use of a bronchoscope to examine the lower airways

Bronchus (plural bronchi): the larger conducting airway that branch from the trachea.

Bronchitis: inflammation of the larger conducting airways, which causes a harsh cough and increased sputum production.

Bronchiolitis: inflammation of the bronchioles, which causes wheezing and coughing.

C

Central Doublet: Pair of microtubules in the center of the cilium that determines the beat direction and orientation.

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

Compound Heterozygote: An individual who has two different abnormal alleles at a particular locus, one on each chromosome of a pair; usually refers to individuals affected with an autosomal recessive disorder.

Cilium (plural clila): Small hair-like projections that line the airway, middle ear, and paranasal sinuses that move rhythmically to clear particulates and bacteria from the lung.

Conductive Hearing Loss: Hearing loss due to middle ear effusions or other problems with the bones of the middle ear

Congenita or Congenital: Occurring at or near birth.

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR): A prominent chloride (salt) channel present at the surface of respiratory epithelia and is dysfunctional in cystic fibrosis.

Cytoplasm: A complex of structures, proteins, and organelles (not including the nucleus) that make up a cell.

D

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

Direct DNA Analysis (or direct DNA): The use of any test method, such as sequence analysis, mutation scanning, or mutation analysis to detect a mutation in a gene

Disease-Causing Mutation: A gene alteration that causes or predisposes an individual to a specific disease.

DNA (or deoxyribonucleic acid): The molecule, which encodes the genes responsible for the structure and function of an organism and allows for transmission of genetic information from one generation to the next.

Dynein Arm: A projectile from the microtubule (inner or outer) and the "motor" of the cilium, providing energy for cilia movement.

E

Effusion: Fluid that has seeped into a body cavity, such as the middle ear.

Electron Microscopy: A high-powered microscope that uses focused electron beams to create a greatly magnified image.

Epithelial Sodium Channel (ENaC): The sodium (salt) channel that is present at the surface of respiratory epithelia and has abnormal function in cystic fibrosis and pseudohypoalsosteronism.

Epithelium: A thin-layer of cells that line the surface of inner organs, including the respiratory tract, which serve as a barrier to the environment.

Exacerbation: The abrupt worsening.

F

Flagellum (Plural Flagella): A slender, whip-like projection that is used by certain cells (e.g., spermatozoa) for locomotion.

G

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 Locus: A specific site on a chromosome.

Genome: The complete DNA sequence, containing all genetic information and supporting proteins, in the chromosomes of an individual or species.

Genotype: The genetic constitution of an organism or cell; also refers to the specific set of alleles inherited at a locus.

Genotype-Phenotype Correlation: The association between the presence of a certain mutation or mutations (genotype) and the resulting pattern of abnormalities (phenotype).

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.

H

Heterotaxy: (syn. 'situs ambiguus') Abnormal distribution or placement of the chest and abdominal organs.   

Heterozygote: An individual who has two different alleles at a particular locus one on each chromosome of a pair; one allele is usually normal and the other abnormal.

Homozygote: An individual who has two identical alleles at a particular locus, one on each chromosome of a pair.

Hydrocephalus: Abnormal increase in cerebrospinal fluid that surrounds the brain which increases the size of the head.

Hypoxemia: Inadequate (low) oxygen level in the blood.

Hypercapnia: Elevated carbon dioxide level in the blood leading to increased acid concentrations (acidosis).

I

Ion Channels: Ion channels are present in the membranes that surround all biological cells. By conducting and controlling the flow of ions, these pore-forming enzymes help establish the small negative voltage that all cells possess at rest (see cell potential). An ion channel is an integral membrane protein or more typically an assembly of several proteins. Such "multi-subunit" assemblies usually involve a circular arrangement of identical or related proteins closely packed around a water-filled pore. Ions move through the pore single file--nearly as fast as the ions move through free fluid. Access to the pore is governed by "gates," which may be opened or closed by chemical or electrical signals, or mechanical force, depending on the variety of channel.

Immotile Cilia Syndrome: Another term for primary ciliary dyskinesia.

Infertility: Inability to produce children.

In-Frame Mutation: A mutation that does not cause a shift in the triplet reading frame; such mutations can, however, lead to the synthesis of an abnormal protein product.

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.

K

Kartagener Syndrome: Primary ciliary dyskinesia associated with situs inversus totalis.

Kartagener Triad: The clinical findings of situs inversus totalis, bronchiectasis, and chronic sinusitis in a patent.

L

Laterality Defect: A term referring to the disruption of typical left-right patterning in organ placement during development leading to situs (organ placement, structure or function) anomalies. (See also situs inversus, situs ambiguus, heterotaxy)

Linkage Analysis: (synonym: indirect DNA analysis) Testing DNA sequence polymorphisms (normal variants) that are near or within a gene of interest to track within a family the inheritance of a disease-causing mutation in a given gene.

M

Malrotation: Abnormal rotation of all or part of an organ, such as the small intestines.

Microtubule: A rod-like structure that in a normal cilium exists as an array of 9 doublets arranged in an outer circle around a central pair.

Middle Ear: A narrow air-filled space between the tympanic membrane (ear drum) and inner ear which contains the three small bones that conduct sounds.

Missense Mutation: A missense mutation is a change in one DNA base pair that changes a codon into a codon corresponding to a different amino acid.

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.

Mucociliary Clearance: the mechanical elimination of fluid, bacteria, and particulates from the respiratory tract, relying on the close coordination of ciliary function, airway surface fluid secretion, and mucin secretion.

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

Mutation Analysis: (synonym: targeted mutation analysis) Testing for the presence of a specific mutation (e.g., Glu6Val for sickle cell anemia), a specific type of mutation (e.g., the trinucleotide repeat expansion associated with spinocerebellar ataxia type 1, deletions associated with Duchenne muscular dystropy), or set of mutations (e.g., a panel of mutations for cystic fibrosis), as opposed to complete gene sequencing or mutation scanning, which detect most mutations in the tested region.

Mutation Screening (Mutational Profiling): A process by which a segment of DNA is screened via one of a variety of methods to identify variant gene region(s). Variant regions are further analyzed (by sequence analysis or mutation analysis) to identify the sequence alteration.

N

Nasal Polyp: A small, pearly-gray, stalk-like growth from the epithelial surface inside the nose.

Nasal Potential Difference: A method for measuring channel function in the nasal epithelium that has been used as a diagnostic technique for cystic fibrosis.

Nonsenses Mutation: A nonsense mutation is a change in one DNA base pair. Instead of substituting one amino acid for another, however, the altered DNA sequence prematurely signals the cell to stop building a protein (i.e. a stop codon). This type of mutation results in a shortened protein that may function improperly or not at all.

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.

Nucleus: A central structure in the cell that contains genetic material (DNA) and controls cellular function and division.

O

Organelle: Specialized structure in the cell.

Otitis Media: Inflammation of the middle ear that results in ear pain and hearing loss.

Outer Doublet: One of nine microtubule pairs on the outside that permits the cilia to beat.

P

Pancreas: An irregularly-shaped gland in the abdomen that secretes digestive enzymes into the duodenum as well as hormones important for the regulation of blood glucose levels (e.g., insulin).

Pancreatitis: Inflammation of the pancreas that causes nausea, vomiting, and intense abdominal or flank pain.

Paroxysm: In medicine, a paroxysm is a violent attack. It may be due to the sudden occurrence of symptoms or the acute exacerbation of preexisting symptoms.

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

Point Mutations: nucleotide substitutions that result in missense mutations, nonsense mutations or deletions and insertions.

R

Radial Spokes: Structures that extend from the central doublet to the surrounding nine outer doublets in a cilium.

Reading Frame: (synonym: exon) A sequence of messenger RNA that is translated into an amino acid chain, three bases at a time, each triplet sequence coding for a single amino acid.

RNA: (synonym: ribonucleic acid) The molecule synthesized from the DNA template; contains the sugar ribose instead of deoxyribose, which is present in DNA; three types of RNA exist, messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

S

Sinusitis: Inflammation of the paranasal sinuses that can cause fever, headache, nasal congestion, and purulent discharge.

Situs ambiguus: (syn. 'situs ambiguous' 'heterotaxy') A Latin term meaning abnormal distribution or placement of the chest and abdominal organs.   

Situs Inversus Totalis: A Latin term meaning the reversed, mirror-image orientation of the inner organs.

Small Intestine: The upper portion of the intestine where digestion occurs and most nutrients are absorbed into the bloodstream, consisting of the duodenum, jejunum, and ileum.

Sputum: Mucus or phlegm coughed up and expelled from the respiratory tract.

T

Trachea: The largest conducting airway, also known as the windpipe.

Transcription: The process of synthesizing messenger RNA (mRNA) from DNA.

Translation: The process of synthesizing an amino acid sequence (protein product) from the messenger RNA code.

Tympanic Membrane: The ear drum.

Tympanostomy Tube: Also known as myingotomy or ear tube, a device designed to equalize pressure between the middle ear and the outside atmosphere, and used as treatment of chronic otitis media.

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