Читать книгу Genetic Analysis of Complex Disease - Группа авторов - Страница 46

Alterations in the genetic code can be neutral, beneficial, or deleterious. Neutral and beneficial changes contribute to the natural variation among individuals and are not considered to have a negative effect on the organism. Rare changes in the genetic code that lead to an abnormal trait or disease phenotype are typically termed a mutation (or a pathogenic variant). The pathology of a mutation can be the result of either a loss or gain of function of the gene product. Such changes can occur in a number of different ways as highlighted below. A polymorphism, on the other hand, is used to describe a genetic variation in which there are two or more possible alleles at a particular locus. A genetic variation is typically termed a polymorphism if it is found in >1% of the population. A polymorphism may be a change in a single nucleotide, known as a single nucleotide polymorphism, an insertion or deletion (indel), or a duplication or deletion of a large segment of DNA, sometimes referred to as a copy number variant (CNV). Much research is currently underway to evaluate the effects of such polymorphisms on common and complex diseases, such as multiple sclerosis, cancer, and heart disease.