A normal mode with substantial variation of a carbonyl bond length. Its wavenumber depends on the effective force constant and coupled motions; substitution, conjugation and measurement conditions matter.

A normal mode involving substantial stretching of a carbon–carbon double bond. conjugated systems alter its force constant and infrared intensity.

An organism or tissue containing cells with different genotypes. Marked clones can separate the tissue requiring a gene product from tissues responding to it.

Dependence of the effect of one genetic change on another. Double-mutant and bypass experiments can order functional requirements, but phenotype suppression alone does not prove a direct molecular interaction.

The sex producing distinct classes of gametes with respect to the sex chromosomes, as with XY males or ZW females in familiar systems.

The number of copies of a gene available in the specified biological cell or genotype. A dosage change can alter an outcome even before duplicated copies diverge in function.

Coexistence of distinct inherited variants in a biological population. Opposing selective effects do not alone guarantee persistence: a protected polymorphism requires the relevant alternatives to increase when rare under the specified model.

epistasis in which the benefit of a mutation tends to be smaller in fitter genetic backgrounds. Its measured magnitude depends on the chosen scale of genotype fitness.

Comparison of lineages raised under standardized conditions. Replicated families and randomized rearing help distinguish inherited differences from immediate environmental effects; persistent maternal effects require additional controls.

Inherited differences among members of a biological population, including alternative alleles and combinations of alleles. Their phenotypic consequences depend on genetic background and environment.

Transmission of a regulatory state beyond the initiating event without requiring a change to the underlying DNA sequence. Persistence over time must be distinguished from continued exposure to the original inducing signal.

A genetic element capable of moving or producing copies that insert at new positions in a genome. Repression of its expression can prevent mobilization before insertional damage occurs.

Genotype-phenotype linkage in experimental selection keeps the sequence encoding a candidate associated with the function used to select it. Clonal compartments or display particles carrying the encoding DNA prevent active products from indiscriminately rescuing unrelated inactive variants.

A short tandem repeat in DNA. Repeat-length changes can arise through DNA polymerase slippage, making both biological instability and amplification artifacts relevant to measurement.

A gene proposed to influence a trait on functional, positional or comparative grounds. Candidate status is not a demonstration of causation.

Restoration of a perturbed phenotype by a specified genetic intervention. Controls must separate restored target function from nonspecific intervention effects.

An offspring or descendant combining ancestry from distinguishable parental lineages. A hybrid can be viable and fertile; its existence alone neither proves nor disproves strong reproductive isolation in natural biological populations.

Genomics studies genomes as integrated sets of sequence and functional elements. It includes genome assembly, genome annotation, variation and comparisons across individuals or species. Whereas a focused genetic experiment can follow one gene, genomics can ask how many regions jointly contribute to a trait. Large-scale measurement makes consistent sampling, reference choice and statistical controls especially important. ^[ref]

An inherited disorder caused by pathogenic variation in beta-globin, classically the haemoglobin-S substitution. Genotyping detects the allele; interpretation also depends on the other inherited globin allele.

Comparison of informative DNA markers for identification or relatedness. Multilocus matches require statistical interpretation and controls for contamination, mixtures and allelic dropout.