Glossary of terms [1]
| Anticipation | Apparent earlier age of onset and increased severity of a disease in successive generations. |
| Complex disease | A disorder in which the cause is considered to be a combination of genetic effects and environmental influences. |
| Monogenic disorder | Disorder caused by one or more mutations in a single gene, e.g. cystic fibrosis. Such disorders are also sometimes referred to as Mendelian diseases. |
| Mutation | A mutation is a change in the DNA sequence. Germline mutations (that occur in eggs and sperm) can be passed on to offspring, while somatic mutations (that occur in body cells) are not passed on. |
| Penetrance | The frequency (in percent) with which a dominant or homozygous recessive gene or gene combination manifests itself in the phenotype of the carriers. |
| Pathogenicity (class) | Each variant found through genetic sequencing is currently classified according to several criteria and reported as benign, likely benign, of unknown significance (“variant of unknown significance”), likely pathogenic or pathogenic. |
| Phenocopy | A phenotypic condition that resembles the trait expressed by a certain genotype, in the absence of carriage of the genotype. |
| Polymorphism | A chromosome or DNA variant that is observed in natural populations. A gene locus is defined as polymorphic if the minor allele has a frequency of 0.01 (1%) or more. The most common type of polymorphism involves variant at a single nucleotide (also called a single nucleotide polymorphism). |
| Predisposition | A genetic alteration that increases an individual's susceptibility or predisposition to a certain disease or disorder. When such a variant (or mutation) is inherited, development of symptoms is more likely, but not certain. |