acclimatization: the manner in which an organism adapts to a new environment or to a change in the old. For microbes, these physiological modifications often involve enzymatic changes (changes that modify proteins that speed up biochemical reactions). These modifications allow the organism to utilize a new nutrient source for survival. [Source: Biotechnology Industry Organization, www.bio.org]

acquired genetic mutation: see somatic cell genetic mutation

additive genetic effects: the effects of alleles at two different loci are additive when their combined effect is equal to the sum of their individual effects. Additive effects are most easily understood in the context of continuous (quantitative) traits. Consider a disease in which two loci, locus 1 with alleles A and a, and locus 1 with alleles B and b, contribute to the phenotype. If each allele represented by a capital letter contributes a score of 2 to the phenotype, and each allele represented by a small letter contributes a score of 3 to the phenotype, then if the alleles at loci 1 and 2 are additive, the resultant pheno-types for the possible genotypes are as follows: AABB - 8; AABb - 9; Aabb - 11; AaBB - 10; AaBb - 10; Aabb - 11; aaBB -10; aaBb - 9; aabb - 12. [Source: NHBLI/NCBI Glossary]

adjuvant: a substance that, in the presence of a drug, speeds up or improves the effectiveness of the medicine. The term is also used to identify a substance that is added to a vaccine so that a smaller dose of the vaccine is needed to induce an antibody response (i.e. an immune system response). The adjuvant accomplishes this by (1) preventing antigens from leaving the area where the immune response is occurring, and (2) by increasing the rate of multiplication of the lymphocytes. [Source: Biotechnology Industry Organization, www.bio.org.]

aerobic: requiring Oxygen (O2) for survival or growth. A good example of an aerobic organism is the human being. [Source: Biotechnology Industry Organization, www.bio.org]

affected relative pair: a general term describing a set of individuals related by blood, each of whom is affected with the trait in question. The most common types of affected relative pairs include affected sibling pairs, affected cousin pairs, and affected avuncular pairs. [Source: NHBLI/NCBI Glossary]

allele: one of a number of different forms of a gene. Each person inherits two alleles for each gene, one allele from each parent. These alleles may be the same or may be different from one another.

allograft: a transplant process wherein a tissue or organ is taken from one individual (donor) and placed into another (recipient). Both donor and recipient are members of the same species. Rejection of the transplanted material is a problem since the donor and recipient do not have the same genetic make up, unlike affected relative pairs. Matching surface antigens and other factors between donor and recipient and the use of anti-rejection drugs can significantly lessen the chance of rejection. Also known as a homograft.

Alzheimer's disease: a disease characterized by, among other things, progressive loss of memory. The development of Alzheimer's disease is thought to be associated at least in part with possessing certain alleles of the gene, which encodes apolipoprotein E.

amino acid: one of twenty different molecules that combine to form proteins. The sequence of amino acids in a protein determines the protein's structure and function.

amplification: an increase in the number of copies of a specific DNA fragment. Polymerase Chain Reaction (PCR) is a cheap and easy technique used to amplify DNA strands by heating and cooling a medium that includes the strand to be copied, DNA polymerase, two 20-base primers, and an excess of nucleotides. Once a copy is made of the original sequence it can be used to generate subsequent copies, thus creating more and more DNA templates that can be used for duplication. [Source: Biotechnology Industry Organization, www.bio.org]

anaerobic: requiring little or no Oxygen (O2) for survival or growth. For instance, there are certain fungi and bacteria types that flourish in conditions that lack the presence of oxygen. [Source: Biotechnology Industry Organization, www.bio.org]

analyte: the substance which a laboratory test aims to detect. In cholesterol testing, for example, the analyte is cholesterol. In genetic testing, the analyte could be, for example, a specific allele or genetic mutation.

antibiotics: a group of chemical substances used to kill or inhibit the growth of certain microorganisms (bacteria, fungi, etc.) Antibiotics are widely used to prevent or treat the spread of infectious disease. They can be produced naturally, using microorganisms, where antibiotics are formed as a metabolic byproduct in bacteria or fungi, or synthetically. [Source: Biotechnology Industry Organization, www.bio.org]

antibody: a protein produced by the immune system in humans and higher animals, which binds to a specific antigen. When antibodies bind to corresponding antigens they set in motion a process to eliminate the antigens.

anticipation: the phenomenon whereby disease severity increases with each passing generation. Since disease severity is often difficult to measure, anticipation is frequently measured in terms of patient-reported age-of-onset of the disorder. For example, in a disease showing anticipation, a child may have earlier onset than their parent who has earlier onset than their grandparent. [Source: NHBLI/NCBI Glossary]

anticodon: a specific three-nucleotide sequence in transfer RNA that is complementary to a codon (a three-nucleotide sequence in messenger RNA) that specifies an amino acid in protein synthesis. When a codon and anticodon bond (because they are complementary strands) the amino acid attached to the transfer RNA is able to connect to the growing amino acid strand, which eventually forms a protein. [Source: Biotechnology Industry Organization, www.bio.org]

antigen: a foreign substance that, when introduced into the body, can stimulate an immune response.

antihemophilic factors: a family of blood plasma proteins that is necessary for the blood-clotting process. This group includes factor VIII, which in most cases of hemophilia, is found to be deficient. When the skin surrounding a body is cut or otherwise disrupted a cascade of these antihemophilic factors, or "clotting factors," are initiated near the problem site. Certain clotting factors cause platelets in the blood to become "sticky" which attach to the wounded site and, in turn block the exit of blood from the body. The clotting factors also induce the binding of fibrin molecules to create an insoluble meshwork clot preventing blood loss. [Source: Biotechnology Industry Organization, www.bio.org]

antisense: a piece of nucleic acid, typically created in the lab, which has a sequence exactly opposite to an mRNA molecule made by the body. mRNA molecules made by the body serve as templates for the synthesis of protein (see transcription). Since the "antisense" mRNA molecule binds tightly to its mirror image, it can prevent a particular protein from being made.

antisense oligonucleotide: a short string of nucleotides that can bond to messenger RNA (mRNA) and block the process of gene expression. [Source: NHBLI/NCBI Glossary]

antiserum: a serum, the liquid portion of the blood without cells, that contains antibodies that are developed to combat specific antigens such as viruses, bacteria, etc. Antibodies can be acquired from an animal that has either been infected with a microorganism that has the antigen or has been injected with the antigen directly into the body. Antisera are used to confer passive immunity to many diseases. [Source: Biotechnology Industry Organization, www.bio.org]

apolipoprotein E (Apo E): certain alleles of the gene which encodes the protein apolipoprotein E have been reported to be associated with the development of heart disease and Alzheimer's disease.

apoptosis: the process which, when functioning normally, programs cells to self-destruct at an appropriate moment in an organism's life-cycle. If the apoptotic process malfunctions in a cell, uncontrolled cell growth may result, which can contribute to the development of cancer. Such disruption of apoptosis may be associated with an inherited genetic mutation or a somatic cell genetic mutation.

application (patent): a nonprovisional utility patent application must include a specification, including a claim or claims; drawings, when necessary; an oath or declaration; and the prescribed filing fee. [Source: "Glossary," USPTO Website www.uspto.org, accessed 1 February 2002.]

artificial insemination: a process whereby semen is placed within a female's uterus by artificial means i.e. other than sexual intercourse. This process is usually accomplished by placing the semen in a syringe and then using the syringe to deposit the semen at the mouth of the uterus. Sperm cells within the semen then travel to and fertilize waiting egg cells. This process is used to treat some forms of human infertility. Artificial insemination is a common practice in the production of domestic livestock. Compare with invitro fertilization, invivo fetilization.

ascertainment: the scheme by which individuals are selected, identified, and recruited for participation in a research study. [Source: NHBLI/NCBI Glossary]

assay: the examination of a compound or mixture in order to determine the amount of a certain component present (like finding out how many eggs are in a cake). An assay can also be used to describe the potency of a given drug when used in a pharmacological context. In toxicology, the term is used to describe a procedure where living cells (i.e. a cell culture) are used to determine the presence of a given chemical, while in virology an assay is used to establish the effectiveness of a virus on a particular host. [Source: Biotechnology Industry Organization, www.bio.org]

association: in human genetic linkage studies, association studies frequently involve the comparison of allele frequencies for a marker locus between a disease population and in a control population. When statistically significant differences in the frequency of an allele(s) are found between a disease and control population, the disease and allele(s) are said to be in association. [Source: NHBLI/NCBI Glossary]

attenuated: weakened; with reference to microbiology or virology, to decrease the effectiveness, or virulence, of a pathogen. When a vaccine is attenuated, it means that it contains a weakened virus. This procedure is commonly used to induce active immunity in the body without causing illness. [Source: Biotechnology Industry Organization, www.bio.org]

autograft: tissue taken from one part of an individual organism's body and then moved or transplanted to another location within that same organism. Rejection is rarely (if ever) a problem since the donor and recipient are the same individual. Skin transplants are a common example. Autografts are also used when bone marrow is harvested from an individual and stored for later use. This marrow tissue is transplanted back into the donor to replace tissue destroyed during chemotherapy.

autoimmune disease: a disease whereby an individual's immune system mounts an attack on a portion of its own tissues. Tissues undergoing such an attack can be destroyed in the process. Rheumatoid arthritis is an example of an autoimmune disease.

autoradiography: a technique that uses X-ray film to visualize radioactively labeled molecules or fragments of molecules; used in analyzing length and number of DNA fragments after they are separated by gel electrophoresis. [Source: DOE Primer on Molecular Genetics]

autosomal recessive disorder: see autosome and recessive allele.

autosome: any chromosome that is not involved in determining an organism's sex. Humans have 22 pairs of autosomes in each cell.

avuncular relationship: the nieces and nephews (or aunts and uncles) of individuals are related in an avuncular fashion. [Source: NHBLI/NCBI Glossary]