HD Glossary

Note: Some words can have differing definitions depending on the context in which they are used. The definitions presented here are the ones that best apply to the words as they are used. HDSA is grateful to the Stanford Hopes website for their contribution and maintenance of this glossary.

 

 

G
  • GA - See geldanamycin.
  • GABA - Also known as Gamma-aminobutyric acid. It is the major inhibitory neurotransmitter of the nervous system.
  • gamete - Cell from an organism that has only one set of chromosomes; also called a "germ cell." Sperm and eggs are both examples.
  • gamma-carbolines - A type of small molecule whose derivatives have recently been associated with antipsychotic, antibiotic and antitumor activity.
  • gamma linoleic acid (GLA) - A breakdown product of linoleic acid (LA) which leads to the production of prostaglandins.
  • gamma wave - The highest frequency and most important type of brain wave; involved in higher mental acuity such as perception and consciousness.
  • ganglia - Plural form of ganglion.
  • ganglion - A group of nerve cell bodies in the Central Nervous System (CNS) or Peripheral Nervous System (PNS). (Plural form: ganglia.)
  • GAPDH - Glyceraldehydephosphate dehydrogenase. A multifunctional protein crucial to cellular glycolysis; interacts with the expanded glutamine region of proteins in neurodegenerative disorders like HD.
  • gastrointestinal - Relating to the stomach and intestines.
  • geldanamycin - a naturally-occurring drug produced by microorganisms. It acts by binding to hsp90, which then allows heat-shock-factor 1 to activate the heat-shock response.
  • gel electrophoresis - A research technique used to separate molecules (or fragments of a molecule) according to size. Upon electrical stimulation, smaller fragments of a molecule will move faster through the gel than larger fragments. The process is typically done to separate DNA fragments after the DNA has been cut with restriction enzymes.
  • gene - A section of DNA that codes for a specific functional product, such as a protein. For example, the Huntington gene codes for the huntingtin protein.
  • gene expression - The process in which a gene is read and its protein is produced. Hence, the gene is "expressed."
  • gene locus - Place on a chromosome where a gene is located. A particular gene is located at the same place on the same chromosome in everyone. Plural: loci.
  • gene silencing - Targeting or interfering with a specific gene and preventing its expression (in other words, preventing it from leading to a protein.)
  • gene splicing - Joining together or inserting segments of DNA or RNA so as to form new genetic combinations or change a genetic structure.
  • gene therapy - The insertion of normal or genetically altered genes into cells usually to replace defective genes. Sometimes used in the treatment of genetic disorders.
  • gene transcription - Another term for transcription.
  • genotyping - Determining the genetic makeup of an organism.
  • generalized seizure - A seizure that involves the entire brain. Generalized seizures are caused by electrical discharges originating from both hemispheres of the brain.
  • generalized tonic-clonic - Tonic-clonic seizures that are generalized, meaning they are caused by discharges from both sides of the brain. Also referred to as grand mal seizures.
  • genetic - Pertaining to genes. Typically used when referring to the study of genes or when the cause of a disease is somehow traced to genes.
  • genetic disorder - any disease that is caused by a mutation in a gene. These diseases are usually heritable, passed from parent to child, although mutations can occur sporadically and begin in a new generation.
  • genetic research cycle - The process of learning about and developing treatments for genetic diseases. The cycle, which begins and ends with patients and their families, includes basic research, applied research, and clinical research.
  • genetic screen - An experiment to look at an organism’s genome to look for which genes cause a certain desired phenotype to appear.
  • geneticist - Someone who studies the relationship between genes and the traits that are observed in living things.
  • genetics - The study of heredity and how traits are passed on through generations.
  • genome - An organism’s complete set of DNA.
  • genotype - The genetic makeup of an organism, distinct from its phenotype.
  • germ cell - A kind of cell that gives rise to the reproductive cells. See also germ line.
  • germ line - A group of cells that contain the organism's genome and give rise to the reproductive cells.
  • Ginkgo biloba - A plant that has been shown to have certain antioxidant, anti-inflammatory, and neuroprotective properties. Currently being studied as a potential treatment for HD.
  • ginkgolide - A component of the terpenoids that have been shown to have anti-inflammatory effects. They also cause a reduction in blood clotting.
  • gland - An organ that produces and releases one or more substances for use in the body.
  • glia - Another term for neuroglia.
  • glial cells - Cells that serve as supporting elements to the brain and act as scavengers, removing debris after injury or neuronal death. They are also responsible for maintaining ionic balance and producing the fatty coating in nerve cells.
  • gliosis - The excess growth of astrocytes in the brain or spinal cord, usually occurring after injury to one of these parts.
  • globus pallidus - One of the components of the basal ganglia. It relays information from the caudate and putamen to the thalamus. It is sometimes called the pallidum.
  • glucocorticoid degenerative cascade - The process that occurs when excess glucocorticoids cause hippocampal nerve cells to die, which then leads to the release of even more glucocorticoids, which then leads to further death of hippocampal nerve cells.
  • glucocorticoid-glucocorticoid receptor complex - Another term for the glucocorticoid-GR complex.
  • glucocorticoid-GR complex - Formed when glucocorticoid hormones bind to glucocorticoid receptors in the cell. Also referred to as glucocorticoid-glucocorticoid receptor complex.
  • glucocorticoid receptors - Receptors found in the cell that contain binding sites for glucocorticoids.
  • glucocorticoids - A group of steroids that have metabolic and anti-inflammatory effects. Glucocorticoid drugs are compounds with effects similar to those of the natural glucocorticoids produced in the body.
  • glucose - The major sugar in the body and a key molecule in energy metabolism.
  • glutamate - An amino acid precursor. Glutamate is the most common excitatory neurotransmitter in the brain and spinal cord.
  • glutamine - The key amino acid in Huntington’s disease. In most people, there are between 10 and 35 sequential glutamines in the huntingtin protein. In people with HD, there are 40 or more copies. Some people with 36-39 copies develop symptoms of HD while others do not. See Table A-1.
  • glutathione - A water-soluble antioxidant, antitoxin, and enzyme co-factor found in animals, plants, and microorganisms. Protects mitochondria against oxidative damage.
  • glutathione peroxidase (GPx) - An enzyme known for its antioxidant effects against peroxides. Its central element is selenium.
  • glycogen - A substance made up of sugars. It is stored in the liver and muscles and releases glucose (sugar) into the blood when needed by cells. Glycogen is the chief source of stored fuel in the body.
  • glycolysis - This process occurs in all organisms, and is responsible for converting glucose to pyruvate and generating ATP in the process. Glycolysis does not require oxygen to function.
  • gonadal ridge - An elevated portion of the developing embryo that contains the primordial germ cells.
  • gossypol - A compound that is believed to decrease the presence of beta-amyloid fibrils, but has little or no success in inhibiting huntingtin protein aggregation.
  • graft-versus-host disease (GVHD) - A condition that results when a donated organ reacts against the recipient’s own tissue; symptoms include skin rash, fever, diarrhea, liver dysfunction, abdominal pain, and loss of appetite.
  • grafting - Transplanting of a portion of cells or tissues.
  • grand mal - Another term for generalized tonic-clonic seizures.
  • granule cells - A specific type of nerve cell that projects information to the cerebellum. This information includes the position and movement of the limbs, as well as the regions of the skin that are being stimulated at any given time.
  • gray matter - Term used to describe an area of the brain that is rich in nerve cell bodies.
  • green fluorescent protein (GFP) - A protein produced by jellyfish that glows when viewed under a specific wavelength of light. Used by researchers as a tool to tag and visualize specific proteins within a cell.
  • GRIK2 (GluR6) - A gene whose functional region codes for a subunit of the glutamate receptor; implicated in age of onset of Huntington’s disease symptoms.
  • growth factors - Proteins that are being tested to see if they prompt nerve growth and brain reorganization.
  • GRP-78 - A protein chaperone that, along with HSP-70, can help regulate protein folding and degradation, as well as help balance calcium levels in cells.
  • guanine - One of the four nitrogenous bases found in DNA; pairs with the base cytosine; often abbreviated as the letter "G"; see Figure B-3.