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Tools for genetics and genomics: Cytogenetics and molecular genetics

Iris Schrijver, MD
James L Zehnder, MD
Athena M Cherry, PhD
Section Editor
Benjamin A Raby, MD, MPH
Deputy Editor
Jennifer S Tirnauer, MD


Intense genetic research has exponentially increased our knowledge of the genetic code of humans and other organisms, leading to the development of numerous methods that facilitate our understanding of normal and abnormal genetic processes. Many of these methods and related techniques are now routinely used in the molecular diagnosis of both inherited disorders and diseases that result from somatic mutations, such as the hematologic malignancies. Molecular genetic and cytogenetic diagnostics are invaluable additions to laboratory testing and clinical evaluation, providing diagnostic, therapeutic, and prognostic information. (See "Genetic abnormalities in hematologic and lymphoid malignancies".)

Although the advent of improved and faster molecular methods has transformed the traditional diagnostic process, keeping current with the most recent advances is daunting [1]. A conceptual approach to a selection of the most common standard and novel diagnostic tools will be applied to this review. An outline of the advantages and limitations of each of the techniques is included, as well as some examples of their applications. A brief introduction to the terms required to properly understand these applications is provided separately. (See "Principles of molecular genetics".)

Three general categories of testing can be distinguished.

Mutation detection of known sequence changes can be performed. This type of testing is targeted and typically limited to a predefined number of sequence changes, selected in advance. Selection is generally based on association with clinical phenotypes. Sequence changes may be located within a single gene or across multiple genes. Depending on the testing method used, the number of included sequence changes can range from a single mutation to thousands of mutations.

Cytogenetic studies of large structural variants are typically performed when the phenotype does not seem limited to point mutations and relatively small deletions and duplications. Such studies are helpful in syndromic phenotypes and for constellations of symptoms typically associated with abnormalities on the scale of chromosomes rather than single exons or genes.

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Literature review current through: Nov 2017. | This topic last updated: Sep 19, 2017.
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