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Basic principles of genetic disease

Benjamin A Raby, MD, MPH
Section Editor
Anne Slavotinek, MBBS, PhD
Deputy Editor
Jennifer S Tirnauer, MD


The importance of genetics and genomics in clinical medicine is increasing.

This topic review presents an overview of the types of genetic and genomic disorders that can occur and the types of tools available to evaluate them, along with links to detailed reviews in UpToDate that discuss these concepts.

Terminology used to describe concepts in genetics and genomics is presented in a glossary. (See "Genetics: Glossary of terms".)

Molecular genetics, including nucleic acid synthesis, RNA transcription, and post-translational modifications, is discussed in greater detail separately. (See "Principles of molecular genetics".)


DNA, RNA, and protein: The building blocks of life — Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are linear, polymerized strands of linked nucleotides (figure 1 and figure 2 and figure 3). A nucleotide is a nucleoside, or a combination of a sugar (ribose or deoxyribose) and a base, that is linked to a phosphate group. RNA differs from DNA in that the hydrogen at the 2' position in DNA is replaced by a less stable hydroxyl group in RNA. There are four DNA bases: adenine (A), cytosine (C), guanine (G), and thymidine (T). In RNA, thymidine is replaced by uracil (U). DNA or RNA polymers are formed by the linking of the 5' phosphate of one nucleotide to the 3' hydroxyl group of another.

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Literature review current through: Nov 2017. | This topic last updated: Oct 02, 2017.
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