Pharmacogenetics
Glossary
Abacavir:
A medicine used in the treatment of HIV/AIDS.
Adverse reaction:
An untoward medical occurrence caused by and arising after the administration of a medicine under normal conditions of use.
Allele:
A variant form of a gene, which differs in DNA sequence from alternative alleles of the same gene.
Amino acid:
A molecule which serves as the building block of proteins. Proteins have different characteristics as determined by the sequence of amino acids. Genes specify this sequence.
Candidate gene:
A gene suspected of contributing to a disease or trait by virtue of knowledge of its function and/or chromosomal position.
Chromosome:
The thread-like DNA in a cell is divided into several separate lengths. Each length forms a structure called a chromosome. Most mammalian cells contain two copies of every chromosome, with the exception of sex chromosomes in males. Human cells contain 23 pairs of chromosomes.
DNA (deoxyribonucleic acid):
The chemical substance of which a gene is made and which encodes genetic information.
Efficacy:
The power of a treatment to have an effect.
Gene:
The fundamental physical and functional unit of heredity consisting of a sequence of DNA, occupying a specific position within the genome.
Gene expression:
The process by which information contained in a gene is transcribed to produce functional RNA molecules which are then translated to produce proteins.
Genetic exceptionalism:
The view that genetic information is qualitatively distinct from other medical information.
Genetic marker:
Any locus that, by virtue of allelic variation between individuals, serves to distinguish one group of chromosomes from another at a particular location. Depending on the context, microsatellites, SNPs and polymorphisms in proteins may all serve as genetic markers.
Genetic test:
A test to detect the presence or absence of, or change in, a particular gene or chromosome. This can be done directly, by analysing the DNA of an individual, or indirectly, by examining the products of their DNA, such as RNA or proteins. In some cases, the presence or absence of particular genes can be determined by consideration of the family history of an individual, or simply by clinical observation.
Genetic variation:
The presence of different combinations of alleles in different individuals in a population.
Genome:
The total genetic complement of an individual or of a species.
Genotype:
An individual’s genotype is their entire genetic constitution, as distinguished from their physical characteristics. See also phenotype.
Glivec (imatinib):
A medicine used in the treatment of chronic myeloid leukaemia.
Haplotype:
A specific combination of linked alleles in a cluster of related genes.
Herceptin (trastuzumab):
A medicine used in the treatment of breast cancer.
Heterozygote:
An individual is said to be a heterozygote when the two alleles at a particular locus are different. 9 4
Homozygote:
An individual is said to be a homozygote when the two alleles at a particular locus are identical.
Locus:
The site of a specific gene on a chromosome.
etabolism:
The process by which the body breaks down and converts medication into active chemical substances.
Metastasis:
The spread of malignant cells from the original site of the cancer to another part of the body.
Molecular genetics:
Molecular genetic methods involve studying genes at the level of the nucleotide sequence.
Mutation:
The modification of a DNA sequence that can potentially result in a change in the function of a gene. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial, or have no effect. If they occur in cells that make eggs or sperm, they can be inherited; if mutations occur in other types of cells, they are not inherited.
Nucleotide:
Nucleotides are the subunits from which DNA and RNA molecules are assembled. A nucleotide is a base molecule (adenine, cytosine, guanine or thymine in DNA; adenine, cytosine, guanine or uracil in RNA), linked to a sugar molecule and phosphate groups. Nucleotides combine in groups of three to code for amino acids.
Orphan medicine:
A medicine used to treat diseases that occur rarely and where there is no hope for recovery of development costs, so there is little financial incentive for industry to develop them.
Over-expression:
Greater than normal production of a gene product, for example a protein or RNA molecule, from a gene. Many animal studies involve the over-expression of a gene in order to determine the function of its product. See also under-expression.
Pharmacodynamics:
How a medicine works in the body.
Pharmacokinetics:
The processes and rate at which a medicine passes through the body.
Pharmacogenetic test:
A test to detect the presence or absence of, or change in, a particular gene or chromosome in order to predict response to a medicine. The test could examine inherited DNA or somatic mutations in DNA.
Pharmacogenetics:
The study of the effects of genetic differences between individuals in their response to medicines. These differences may or may not be related to the disease being treated. The research involves comparing the genotypes of individuals who have different responses to a medicine.
Pharmacogenomics:
This term is not distinctly differentiated from pharmacogenetics, but implies the examination of whole genomes or substantial numbers of genes in order, for example, to identify putative targets for medicines or to identify large-scale differences in the patterns of gene expression in response to chemical compounds.
Pharmacology:
The study of how a medicine acts in the body. It involves the consideration of both pharmacokinetics and pharmacodynamics.
Phenotype:
The observable or measurable traits of an individual as produced by its genotype and the environment.
Polygenic:
A disease or trait is said to be polygenic when it is influenced by more than one gene.
Polymorphism:
Where two or more alleles exist for a gene, such that at least two of the alleles are present in more than 1% of the chromosomes in a population.
Protein:
Proteins are biological molecules that are essential for all life processes and are encoded by an organism’s genome. A protein consists of chains of amino acid subunits and its function depends on its three-dimensional structure, which is determined by its amino acid sequence.
RNA (ribonucleic acid):
A single stranded nucleic acid molecule comprising a linear chain made from four nucleotides, whose sequence determines the informational content of the molecule. RNA is produced by transcription from DNA and may either be translated into protein or may itself play a functional role.
Quality Adjusted Life Years (QALYs):
An arithmetic product of the number of life years gained by an intervention and the quality of life during these years. In effect the value of an added year is adjusted to take into account deterioration in the quality of life.
Single nucleotide polymorphism (SNP):
SNPs are single DNA base pair variations. In genetic research they may be used as genetic markers to locate genes that cause disease or influence other traits. Most SNPs fall within the non-coding regions of human DNA and make no difference to the individual.
Transcription:
The process by which a gene’s DNA sequence is copied into RNA.
Translation:
The process by which RNA directs the synthesis of a protein.
Under-expression:
Lower than normal production of a gene product from a gene. See also overexpression.