GLOSSARY

Words followed by this symbol are defined here

allele--- one of the alternative forms of any gene on a chromosome. Each allele represents a different variation of a physical trait and each has one corresponding allele on the chromosome’s paired counterpart. For example, one blue-eye allele will have one corresponding allele that carries either a blue, green or browneye trait. body condition score (BCS)---a designation, based on a nine-point numeric scale, indicating the amount of fat on a horse’s body. A BCS is assigned after a visual and hands-on appraisal. chromosome--- the self-replicating genetic structure of cells containing the cellular DNA that bears in its nucleotide sequence the linear array of genes. Each species has a constant number of chromosomes set in pairs in the nucleus of each body cell; the horse has 64, or 32 pairs. DNA (deoxyribonucleic acid)---large organic molecule that consists of two chains of nucleotides wound around each other; the material of which genes are made. Genes are responsible for the individual inherited characteristics of living organisms. eastern equine encephalomyelitis (EEE, encephalomyelitis)---brain and spinal-cord inflammation in horses, caused by a specific viral strain transmitted by mosquitoes. EEE is characterized by fever and/or stupor and is almost always fatal. edema--- abnormal collection of fluid (soft swelling) in body tissues. genotype--- total genetic inheritance; all of the genes present in the chromosomes of a horse’s cells, one-half of which came from his father and one-half from his mother. heterozygous--- having two different genes for a characteristic, one of which usually dominates the other. homozygous--- having two identical genes for a characteristic. larynx (voice box)---organ that functions to keep unwanted substances out of the airway and to produce voice; centered just at the back of the lower jawbone, the larynx is equivalent to the human “Adam’s apple.” nonsteroidal anti-inflammatory drug (NSAID)---drug that contains no steroids and acts to reduce heat and swelling. phenotype--- physical makeup and appearance of an organism as determined by its genes and environment; expression of a genotype. rabies--- acute infectious viral disease of the central nervous system, usually fatal. rainrot (rain scald)---crusted, painful, infectious skin inflammation, caused by Dermatophilus congolensis, which lifts the hair and removes it at its root, resulting in slipping away of affected areas of the hair coat; triggered by moisture. RNA (ribonucleic acid)---gene-like chemical found in the nucleus and cytoplasm of cells; plays an important role in protein synthesis and other chemical activities of the cell. There are several classes of RNA molecules, including messenger RNA, transfer RNA and ribosomal RNA, each serving a different purpose. shock--- failure of the vital body systems, characterized by loss of blood volume and pressure, shallow breathing and rapid heartbeat. Shock is usually the direct and potentially fatal byproduct of extremely serious injury, stress or illness. stocking up (stagnation edema)---thickening of the lower leg due to collection of fluid in and under the skin. tetanus--- rigid paralytic disease caused by Clostridium tetani, an anaerobic bacterium that lives in soil and feces. tying up (recurrent exertional rhabdomyolysis, azoturia, Monday-morning sickness, myositis) ---severe, painful cramping of large muscle masses, resulting in discoloration of the urine with the byproducts of muscle destruction. Tying up often is seen in fit horses who resume heavy exercise after a few days of rest without any reduction in grain ration. western equine encephalomyelitis (WEE)--brain and spinal-cord inflammation in horses, caused by a specific viral strain transmitted by mosquitoes. Signs include fever, depression, ataxia and head-pressing. West Nile virus--- flavivirus transmitted by mosquitoes. West Nile virus can infect birds, horses, humans and other mammals. West Nile infection sometimes triggers swelling of the brain (encephalitis) that produces limb weakness, muscle fasciculation (twitching), incoordination, behavioral changes, paralysis and recumbency. In severe cases, West Nile encephalitis can lead to coma and death.