Designed to help learners at any level better understand genetic terms
Guided by national science standards
Explained by scientists at the NIH
The National Human Genome Research Institute (NHGRI) created the Talking Glossary of Genetic Terms to help everyone understand the terms and concepts used in genetic research. In addition to definitions, specialists in the field of genetics share their descriptions of terms, and many terms include images, animation and links to related terms.
— pneumonia caused by the drawing of a foreign substance, such as the gastric contents, into the bronchial tree during inhalation.
ataxic gait — an unsteady, uncoordinated walk, employing a wide base and the feet thrown out.
athetosis — repetitive involuntary, slow, sinuous, writhing motions, especially severe in the hands.
autonomic involvement — what your body does automatically without conscious effort (heart beating, temperature regulation, breathing). Some NBIA individuals have problems involving these functions, such as temperature fluctuations, as their disease progresses.
autosomal recessive inheritance — because most of our genes exist in pairs (one coming from the mother and one coming from the father), we normally carry two working copies of each gene. When one copy of a recessive gene has a change (mutation) in it, the person should still have normal health. That person is called a carrier. Recessive diseases only occur when both parents are carriers for the same condition and then pass their changed genes on to their child. Statistically, there is a one in four chance that two carriers would have an affected child, a two in four chance to have a child who is also a carrier, and a one in four chance to have a child who did not receive the gene mutation.
benzodiazepines — (Valium, Librium, Xanax, Ativan) are a type of antianxiety drugs that help relieve nervousness, tension, and other symptoms by slowing the central nervous system. Some also help to control muscles spasms for NBIA individuals.
blepharospasm — spasmodic blinking and closing of the eyelid caused by the involuntary contraction of the eyelid muscle.
botulinum toxin — a neurotoxin made by Clostridium botulinum; causes paralysis in high doses, but is used medically in small, localized doses to treat disorders associated with involuntary muscle contraction and spasms, in addition to strabismus. Injected into muscles, it can cause temporary weakness of muscles that have involuntary contractions causing pain, twisting, abnormal posture, or changes in person’s voice or speech, relieving pain for a few months at a time.
bradykinesia — extreme slowness in movement.
cerebellar atrophy — general loss of brain cells and tissue in the cerebellar area of the brain.
cerebral atrophy — general loss of brain cells and tissue in the cerebral area of the brain.
chorea — the ceaseless occurrence of involuntary, rapid, jerky, involuntary movements.
choreoathetosis — a condition characterized by involuntary, rapid, jerky movements (chorea) occurring in association with relatively slow, sinuous, writhing motions (athetosis).
corpus striatum — a subcortical mass of gray and white substance in front of and lateral to the thalamus in each cerebral hemisphere.
corticospinal tract — a tract of nerve cells that carries motor commands from the brain to the spinal cord.
de novo mutation — (de novo means anew.) there is an alteration in a gene that is new in the affected individual and was not inherited from either parent. This can happen in a germ cell (egg or sperm) from one of the parents or in the fertilized egg itself.
deep brain stimulation (DBS) — performed by implanting electrodes into the brain with a patient programmable device (neurostimulator) under the skin of the chest or abdomen. The neurostimulator sends pulses to targeted areas of the brain and takes “off line” the part of the brain that is sending too many signals and causing the muscles to move in painful ways as they do in dystonia.
dominant inheritance — an individual has one working copy and one copy of the gene that has a change or mutation. This single mutation is enough to cause the disease. There is a one in two chance (50%) that an affected individual will pass the gene change on to any of his/her children. Most individuals with a dominant disorder have one parent who is also affected.
dopaminergic agents — relating to, involved in, or initiated by the neurotransmitter activity of dopamine or related substances. Dopamine is a brain chemical called a neurotransmitter that carries signals between nerve cells and helps the brain perform critical functions. Dopamine helps the brain control motor functions and movement and possibly to perform other functions related to mood. An imbalance or shortage of dopamine can cause brain dysfunction and disease.
dysarthria — a speech disorder caused by involuntary muscle cramping that affects the muscles in the mouth and throat causing poor articulation and slurring.
dyskinesias — a movement disorder which consists of adverse effects, including diminished voluntary movements and the presence of involuntary movements. Dyskinesia can be anything from a slight tremor of the hands to uncontrollable movement of, most commonly, the upper body, but can also be seen in the lower extremities.
dysphagia — involuntary muscle cramping that affects the muscles in the mouth and throat causing difficulty swallowing.
dystonia — one of the dyskinesias. Dystonia is a neurological movement disorder in which involuntary sustained muscle cramping/contractions may force certain body parts into unusual, and sometimes painful, movements and positions. Dystonia may affect a single body area or be generalized throughout multiple muscle groups. Although there are several forms of dystonia and the symptoms may outwardly appear quite different, the element that all forms share is the repetitive, patterned, and often twisting involuntary muscle contractions.
dystonia-parkinsonism — characterized by the abrupt onset of slowness of movement (parkinsonism) and dystonic symptoms.
dystonic storm — continuous, unremitting, severe dystonic movements, either worsening on a background of dystonia or beginning anew. It can last at least hours to days, producing severe physical and psychological distress.
electroretinogram — device that detects eye changes.
extensor toe signs — indicate damage to the central nervous system. To a painful, pricking stimulus on the sole of the foot: (1) The healthy side shows flexion of thigh, leg, foot, and toes; (2) The paralyzed side shows flexion of thigh, leg, foot, but the toes extended.
eye of the tiger sign — seen on an MRI caused by excess iron deposition in the globus pallidus. Almost always seen in Pantothenate Kinase-Associated Neurodegeneration (PKAN).
fat (lipid) metabolism — lipids are absorbed from the intestine and undergo digestion and metabolism before they can be utilized by the body. Most of the dietary lipids are fats and complex molecules that the body needs to break down in order to utilize and derive energy from.
ferriprox — brand name for the drug deferiprone, an oral drug that chelates iron, and is the focus of a clinical trial for PKAN to determine if it is helpful for NBIA disorders.
freezing — term used to describe movement that stops during ambulation, especially when turning corners or encountering surface variations.
gastrostomy tube — medical device used to provide nutrition to patients who cannot obtain nutrition by mouth, are unable to swallow safely, or need nutritional supplementation. The state of being fed by a feeding tube is called gavage, enteral feeding or tube feeding.
gene mutations — changes within a gene that may cause disease
global developmental delay — Global Developmental Delay (GDD) is the general term used to describe a condition that occurs during the developmental period of a child between birth and 18 years. It is usually defined by the child being diagnosed with having a lower intellectual functioning than what is perceived as ‘normal’. It is usually accompanied by having significant limitations in communication. It is said to affect about 1-3% of the population.
globus pallidus — a structure in the brain involved in the regulation of voluntary movement. It is part of the basal ganglia, which, among many other things, regulate movements that occur on the subconscious level. If the globus pallidus is damaged, it can cause movement disorders, as its regulatory function will be impaired. When it comes to regulation of movement, the globus pallidus has a primarily inhibitory action that balances the excitatory action of the cerebellum. These two systems are designed to work in harmony with each other to allow people to move smoothly, with even, controlled movements. Imbalances can result in tremors, jerks, and other movement problems, as seen in some people with progressive neurological disorders characterized by symptoms like tremors and dystonia.
gonadal dysfunction — or hypogonadism is the condition more prevalent in males in which the production of sex hormones and germ cells are inadequate.
hyperreflexia — an exaggerated response of the deep tendon reflexes, usually resulting from injury to the central nervous system or metabolic disease. Also called autonomic dysreflexia.
hyperintense — when an abnormality is bright (white) on MRI.
hypointense globus pallidus — radiographic evidence of increased amounts of iron in the globus pallidus. Hypointense (less intense): If an abnormality is dark on MRI, we describe it as hypointense.
hypotonia — floppy or low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength.
intrathecal baclofen pump — involves injecting the drug baclofen into the fluid-filled area surrounding the spinal cord. This area is called the intrathecal space. A programmable pump and catheter are surgically placed inside the body and deliver the baclofen continuously based on the settings deemed appropriate by your doctor.
iron chelation — the administration of chelating agents to remove iron from the body. Since the 1970s, iron chelation therapy has been used to treat excess iron stores in the blood. The iron in NBIA is stored in the brain, so it requires a chelator that can cross the blood brain barrier to be effective, such as deferiprone.
lewy bodies — abnormal aggregates of protein that develop inside nerve cells in the brain in Parkinson's disease (PD), Lewy body dementia and some other disorders, including NBIA.
lewy neurites — abnormal clusters of protein that develop inside the nerve cells
muscular rigidity — an alteration of muscle tone in which the muscles are in an involuntary state of continual tension. Muscle rigidity can be a manifestation of neurological damage (basal ganglia diseases) or a side effect of certain medications. Muscle rigidity is the continuous, tonic contraction of the skeletal muscles, often more marked in the flexor muscles than extensors.
neuropsychiatric — mental disorder due to disease of the nervous system.
nyctalopia — night blindness.
nystagmus — rapid involuntary eye movements.
occult bone fracture — fracture without apparent trauma that may be caused by the combination of osteopenia in a non-ambulatory individual with marked stress on long bones from dystonia.
opisthotonos — backward arching C from dystonia. The person is usually rigid and arches the back, with the head thrown backward. If a person with opisthotonos lies on his or her back, only the back of the head and the heels touch the supporting surface.
optic atrophy — affects the optic nerve, which sends messages between the retina and the brain. When the nerve is damaged or breaks down, vision can become blurry, side vision or color vision may be abnormal, the pupil may not work properly, or there may be decreased lightness in one eye compared to the other. Eventually, optic atrophy can cause blindness.
osteopenia — a condition where bone mineral density is lower than normal, with a T score between -1.0 and -2.5
osteoporosis — a progressive bone disease that's characterized by a decrease in bone mass and density and that leads to an increased risk of fracture. Osteoporosis is defined by the World Health Organization (WHO) as a bone mineral density of 2.5 standard deviations or more below the mean peak bone mass.
palilalia — speech disorder characterized by the involuntary repetition of syllables, words, or phrases.
parkinsonism — a neurological syndrome marked by tremor, slowness, rigidity and poor balance. The underlying causes of parkinsonism are numerous, and diagnosis can be complex. The neurodegenerative condition Parkinson's disease (PD) is the most common cause of parkinsonism but it is also seen in some of the NBIA disorders.
paroxysmal — a fit, attack, or sudden increase or recurrence of symptoms (as of a disease).
phenotypes — is the composite of an organism's observable characteristics or traits, such as its morphology, development, biochemical or physiological properties, phenology, behavior, and products of behavior. It is used when describing the traits of a disease.
pre-implantation genetic diagnosis (PGD) — refers to genetic profiling of embryos prior to implantation.
psychomotor regression — loss of previously acquired milestones.
retinitis pigmentosa — an inherited, degenerative eye disease that causes severe vision impairment and sometimes blindness . It is common in the classic form of PKAN.
spasticity — stiffness because of continuous resistance to muscle relaxing, Reflexes (for example, a knee-jerk reflex) are stronger or exaggerated. Spasticity is usually caused by damage to the part of the brain that is involved in movements under your control. It may also occur from damage to the nerves that go from the brain to the spinal cord. Severe, long-term spasticity may lead to contracture of muscles, which can reduce range of motion or leave the joints bent.
spheroids, spheroid bodies, or axonal spheroids — nerve cells have long extensions, called axons that transmit messages from one nerve cell to the next. In NBIA, some axons are found to be swollen with collections of cellular debris or “junk” that should not be there.
strabismus — crossed eyes.
substantia nigra — a brain structure located in the mesencephalon (midbrain) that plays an important role in reward, addiction, and movement. Substantia nigra is Latin for "black substance", reflecting the fact that parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in dopaminergic neurons. Some NBIA individuals have iron deposits in this area.
systemic iron deficiency — systemic denotes the part of the circulatory system concerned with the transportation of oxygen to and carbon dioxide from the body in general, esp. as distinct from the pulmonary part concerned with the transportation of oxygen from and carbon dioxide to the lungs. Systenic iron deficiency is low iron affecting the body generally.
tachylalia — extremely rapid speech.
torticollis — a condition in which there are involuntary contractions of neck muscles resulting in abnormal movements and positions of the head and neck.
transdermal scopolamine patch — a scopolamine patch placed on the skin behind the ear used to control excessive mouth secretions, drooling, nausea, and vomiting. Each patch is good for 3 days.
white matter changes in the brain — changes in white matter known as amyloid plaques are associated with Alzheimer's disease and other neurodegenerative diseases. White matter injuries ("axonal shearing") may be reversible, while gray matter regeneration is less likely.