Genetic Testing Terms
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Adenine – One of four chemical bases in DNA; adenine pairs with thymine to form the DNA double helix.
Carrier – An individual who carries and is capable of passing on a genetic mutation associated with a disease and may or may not display disease symptoms.
Chromosome – An organized package of DNA found in the nucleus of the cell.
Cytosine – One of four chemical bases in DNA; cytosine pairs with guanine to form the DNA double helix.
Deoxyribonucleic Acid (DNA) – The molecule that carries genetic instructions in all living things. DNA is a double-stranded nucleic acid composed of adenine, cytosine, guanine, and thymine.
Diploid – A cell or organism that has paired chromosomes, one from each parent.
Dominant – The version of two or more copies of a gene that is expressed and masks the expression of the other version.
Exon – The coding regions of a gene.
Gene – A segment of DNA that contains information encoding a protein, together with regulatory elements that control gene expression.
Genetic Predisposition – A susceptibility to disease that is related to a genetic condition, which may or may not result in actual development of the disease.
Genome – The entire set of genetic instructions found in a cell.
Genotype – An individual’s collection of genes; genotype also can refer to the two alleles an individual has for a particular gene or genetic marker.
Guanine – One of four chemical bases in DNA; guanine pairs with cytosine to form the DNA double helix.
Haploid – A cell or organism having a single set of chromosomes.
Histocompatibility – Tissue compatibility as determined by genetic variants in the HLA genes located on chromosome 6.
Hybridize – The process of combining two complementary single-stranded DNA or RNA molecules and allowing them to form a single double-stranded molecule through base pairing.
Intron – The non-coding regions between exons of a gene.
Laboratory-Developed Tests (LDTs) – LDTs are in vitro diagnostic tests that are developed, validated, and used for in-house diagnostic purposes; LDTs are intended for use only by the laboratory where they are developed.
Metabolome – All of the metabolites, or small molecules, expressed by an individual cell or organism at a particular point in time.
Microarray – A tool used to sift through and analyze the information contained within a genome. A microarray consists of different nucleic acid probes that are chemically attached to a substrate, which can be a microchip, a glass slide, or a microsphere-size bead.
Mitochondrial DNA – The small circular chromosome found inside mitochondria (organelles found in cells that are the sites of energy).
Nucleotide – The basic building block of nucleic acids consisting of a sugar (either ribose or deoxyribose), a phosphate molecular, and a base.
Nutrigenetic – The study of genetic variants between individuals looking at the interaction between diet and disease.
Nutrigenomic – The study of the impact of nutrients on the genome, proteome, and metabolome.
Pedigree – A genetic representation of a family tree.
Pharmacogenetics/Pharmacogenomics – A branch of pharmacology concerned with using DNA and amino acid sequence data to inform drug development and testing. An important application of pharmacogenomics is correlating individual genetic variation with drug responses.
Phenotype – An individual’s observable traits, such as height, eye color, and blood type.
Polymorphism – One of two or more variants of a particular DNA sequence.
Proteome – The full complement of proteins produced by a particular genome.
Recessive – The version of a gene that is not expressed unless it is present on both copies of the gene (i.e., both alleles are the recessive allele).
Ribonucleic Acid (RNA) – A single-stranded nucleic acid composed of adenine, uracil, cytosine, and guanine residues. Different types of RNA exist, including messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
Short Tandem Repeat (STR) – A region of DNA where a pattern of two or more nucleotides are repeated. The number of repeating segments varies between individuals and some STRs are used for identity testing.
Single Nucleotide Polymorphism (SNP) – A type of polymorphism involving variation of a single base pair.
SNP Microarray – A type of DNA microarray that is used to detect polymorphisms within a population or individual.
Thymine – One of four chemical bases in DNA; thymine pairs with adenine to form the DNA double helix.
Translocation – The rearrangement of chromosome segments such that a portion of one chromosome is moved to another chromosome or another region of the same chromosome.
Variant – A nucleotide sequence that differs from the “normal” (or most common) sequence for a given region of the genome. Variants can include substitutions of one nucleotide for another or insertions or deletions of nucleotides. Variants may be pathogenic, benign, or of unknown clinical significance. The term “variant” does not itself suggest a functional implication for the genetic change.
Reference: National Human Genome Research Institute, 2010. Genome.gov | Talking Glossary of Genetic Terms. Available at: http://www.genome.gov/glossary/index.cfm? Accessed December 3, 2010.