A genomic locus containing repeated short sequence units. Allele length variation allows identification by amplification and fragment analysis, subject to stutter and amplification bias.

Human genetics studies inherited variation and its biological consequences in humans. It connects pedigrees, molecular analysis and population genetics to questions about ancestry, development and disease. Family segregation can identify an inheritance pattern, while a biological population association identifies correlation with a variant or linked region. Neither automatically supplies the molecular mechanism: functional measurements are needed to establish how a variant changes a process. ^[ref]

An elevated propensity to acquire changes in nucleotide sequence, chromosome structure or chromosome number. A fixed alteration alone does not demonstrate a high ongoing alteration rate.

An inherited disorder is a disorder associated with a genetic variant transmitted from a parent. Dominant, recessive and sex-linked patterns describe different relationships between inheritance and expression. Inherited risk need not imply certainty of disease because penetrance, other genes and environment can affect the outcome. A genetic condition caused by a new mutation in an individual is genetic without necessarily having been inherited from a parent. ^[ref]

Inheritance of genetic material outside the nuclear chromosomes, often through only one parent. Its transmission interests can differ from those of biparentally inherited elements.

Genetic rescue is an improvement in biological population fitness associated with introduction of genetic variation, often through gene flow into an inbred biological population. It differs from merely increasing numbers by adding individuals: the genetic contribution must improve descendant performance. The Florida panther restoration provided an empirical case in which introduced ancestry was followed by increased heterozygosity and improved survival measures. Outcomes depend on compatibility and ecological conditions, rather than making every introduction beneficial. ^[ref]

Study of gene functions and interactions using perturbations and genome-scale measurements. Expression correlation and causal requirement are different forms of evidence.

Genome evolution is change in the sequence, content and organization of genomes across generations. Mutation, gene duplication, deletion, genetic recombination and natural selection can change both individual sites and large regions. A duplicated gene can retain its original function, acquire a new role or lose function. Comparing related genomes helps distinguish these histories, but the history of one gene need not match the history of the whole species. ^[ref]

A binding assay that detects a change in electrophoretic mobility when a ligand associates with a labelled target, such as an RNA–protein complex. A concentration series and competition controls help distinguish specific binding from aggregation or non-specific retention.

Electrophoretic separation in a polyacrylamide matrix. Native conditions can preserve molecular complexes, whereas denaturing conditions address different separation goals.

A methoxy group is $-\mathrm{OC}{\mathrm{H}}_3$, a methyl group attached to the rest of a molecule through oxygen. It is an alkoxy substituent and must be distinguished from an attached hydroxyl group.

On an aromatic ring, its oxygen lone pairs can donate into the conjugated system. At the same time, oxygen's electronegativity produces inductive effects, so different electronic contributions must be separated when predicting reactivity.

A nitro group is the functional group $-\mathrm{N}{\mathrm{O}}_2$ attached through nitrogen. Its bonding is described using delocalization and charge-separated resonance forms rather than two independent ordinary nitrogen-oxygen double bonds.

It commonly withdraws electron density from an attached organic framework. This can alter aromatic substitution patterns, acidity of neighboring carbon-hydrogen groups, and optical properties in conjugated molecules.

An ethoxy group is $-\mathrm{OC}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_3$. An aryl ethoxy group can donate an oxygen lone pair into an aromatic ring.

A sulfone contains an $\mathrm{R}-\mathrm{S}(\mathrm{O}{)}_2-R\prime$ group. An aryl sulfone withdraws electron density and commonly directs electrophilic aromatic substitution to meta positions.

A sulfoxide has two carbon substituents, an oxygen and a stereochemically relevant lone pair at sulfur. Different carbon substituents can make sulfur a configurationally persistent stereogenic centre.

A sulfonic-acid-derived anion or group, with negative charge delocalized over oxygen atoms. Carbon–oxygen substitution of an alkyl sulfonate differs from attack at sulfur.

The group PhCH2CH2−, distinct from benzyl PhCH2−. Counting the two carbons between a phenyl group and the attachment site prevents a common synthetic-target error.

The CH3− structural group, with the dash indicating attachment rather than a negative charge when used as a group formula.

A divalent CH2 unit within a structure. Its two hydrogens can be equivalent or nonequivalent depending on symmetry, stereochemistry and environment.

The group PhCH2−, distinct from the two-carbon linker in a phenethyl group.