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.

 

 

D
  • daf-2 - A gene found in roundworms that allows this organism’s cells to respond to a hormone similar to human insulin. Daf-2 controls at least 100 other genes, some of which ward off disease; others act as antioxidants, protecting the worms against damage over time from free radicals in the environment.
  • daughter cells - The cells that result from the reproductive division of one cell during mitosis or meiosis.
  • degenerative / degeneration - The deterioration of a tissue or an organ in which its function is diminished or its structure is impaired.
  • degrade - to break something down. Usually to break a protein down into the original amino acids that were used to build it.
  • delta-5 desaturase - An enzyme necessary for the production of either eicosapentaenoic acid (EPA) or arachidonic acid (AA).
  • delta wave - The slowest type of brain wave; occurs during sleep.
  • dementia - A progressive decline in mental function.
  • dendrites - Short projections on the neuron that receive signals from other neurons. Neurotransmitters bind to receptors located on the surface of dendrites, causing changes within the nerve cell. See Figure D-2.
  • dentate nucleus - A group of nerve cell bodies deep inside the cerebellum; plays a role in the control of skilled, rapid movement.
  • dentate gyrus - A part of the hippocampal formation.
  • Dentatorubro-pallidoluysian atrophy (DRPLA) - A CAG trinucleotide repeat disorder that is characterized by abrupt muscle jerking, involuntary movements, and eventual dementia. For more information, click here.
  • deoxyribonucleic acid - For definition, see DNA.
  • deoxyribose - The particular sugar molecule that is found in DNA.
  • dexamethasone - A glucocorticoid drug with high glucocorticoid activity and low mineralocorticoid activity that is therefore relatively safe to use in high doses.
  • DGLA - Abbreviation for Dihommogamma-Linoleic Acid.
  • DHA - Abbreviation for docosahexaenoic acid.
  • diabetes mellitus - A chronic disease that renders the body unable to use carbohydrates (sugars) properly. This condition affects many organs and body functions, especially those involved in metabolism. Diabetes is characterized by increased levels of glucose (sugars) in the blood.
  • diagnose - To determine the nature of a pathological condition; to recognize a disease.
  • differentiate - The process that cells undergo as they mature to have distinct characteristics and functions.
  • digestive system - The organs that take in food and turn it into products that the body can use to stay healthy. Waste products the body cannot use leave the body through bowel movements. The digestive system includes the salivary glands, mouth, esophagus, stomach, liver, pancreas, gallbladder, small and large intestines, and rectum.
  • dihommogamma-linoleic acid (DGLA) - An omega-6 fatty acid that can be converted into arachidonic acid (AA).
  • dilution - The process of making something weaker or less concentrated.
  • dimer - A molecule that is made of two monomers bound together.
  • diploid - Containing two of each type of chromosome and therefore two alleles for each gene.
  • disaccharide - A molecule made out of two simple sugars. Examples include sucrose and lactose.
  • diuretic - A drug used to increase urine formation and output. Diuretics are prescribed for the treatment of edema (the accumulation of excess fluids in the tissues of the body), which often occurs as the result of disease of the kidneys, liver, lungs, or heart. Diuretics are also used to treat hypertension (high blood pressure).
  • divided attention - the ability to split one’s attention between more than one task. Many HD patients often have trouble with divided attention.
  • DNA - Abbreviation for deoxyribonucleic acid. The molecule of heredity; composed of many nucleotide subunits arranged in a long chain.
  • DNA Polymerase - An enzyme used to make new copies of DNA during replication.
  • docosahexaenoic acid (DHA) - A member of the omega-3 family of fatty acids. It is one of the breakdown products of alpha-linolenic acid (ALA) and is essential to nervous system development and maintenance.
  • domain - A region of a polypeptide chain that independently folds into a structural unit within a protein.
  • dominance - Used to describe a pattern of inheritance in which the dominant allele will be always be expressed, even in the presence of a recessive allele.
  • dominant - An allele whose effect is visible in the heterozygote (mixed) state
  • dopamine - An important neurotransmitter in the nervous system. Nerve cells that release dopamine are most affected in people with Parkinson’s Disease, and are becoming increasingly implicated in HD.
  • dorsal root ganglion - A group of sensory nerve cell bodies. They pass sensory information to neurons in the spinal cord so it can be analyzed by the brain.
  • dose [response relationship - The relationship between the dose of the drug and the changes of symptoms and responses of the body. The response could increase exponentially or linearly as the dose of the drug is increased.
  • dose-dependent - Refers to findings in which the effects of a drug change when people consume a higher or lower amount of the drug.
  • dose response - A relationship in which a change in the amount, intensity, or duration of an exposure is associated with either an increase or decrease in risk of a specified health outcome.
  • double blind - A study in which neither the investigator nor the participant are aware of which treatment a participant is receiving (ie experimental or control). Independent monitors keep track of who gets each type of treatment, and only inform the investigators and participants after all subjects have completed treatment and all measurements have been made. Double-blind trials are thought to produce objective results.
  • double helix - The form in which DNA is most often found in living cells; consists of two complementary single strands of DNA, spiraling around one another; see Figures B-7 and B-1.
  • Drosophila - The common fruit-fly, whose full name is Drosophila Melanogaster, is often used as an animal model in scientific experiments.
  • drugable - For a biological target to be drugable, it must be able to be modified (usually changing the shape, function, or the active site of the protein) by some other molecule that might serve as a therapeutic drug.
  • drug candidates - Chemical compounds that have potential to be developed into a therapeutic drug. Not all drug candidates become products.
  • drug target - A molecule that can be expected to enhance or inhibit a disease.
  • drug therapy - The use of a chemical compound or molecule to treat a disease
  • dry lab - Refers to experiments not performed at the lab bench.
  • dyskinesia - An impairment in voluntary movement ability.
  • dysmorphology - Altered development.
  • dystonia - Prolonged muscle contractions.