Protein deamidation converts an amide-bearing side chain, commonly asparagine or glutamine, into a carboxyl-containing product. It can occur spontaneously or through catalysis and can alter charge, structure or molecular interactions. Some asparagine reactions also produce an altered backbone linkage, making the product chemically more complex than a simple residue replacement. Sample handling and elapsed time can therefore affect the observed modification pattern. ^[ref]

A covalent modification of a histone. Its genomic distribution and associated regulatory state do not by themselves specify chromatin accessibility or causation.

For the dimensionless-spin Hamiltonian $A{\mathbf{S}}_e\cdot {\mathbf{S}}_p+2{\mu }_{B}B(S_{ez}-S_{pz})$, the two aligned-spin states remain at $A/4$. The two states of total spin projection zero mix and have the displayed energies. The parameter $4{\mu }_{B}B/A$ compares off-diagonal Zeeman mixing in the singlet-triplet basis with half the zero-field splitting. A crossover is gradual, not a level-crossing phase transition.

Persistence of a position-associated cellular identity after the original spatial context or instructive signal changes. It is distinct from simply retaining a differentiated tissue identity.

A model in which a phenotype is a point in a multidimensional trait space and genotype fitness declines with displacement from an optimum. With displacement $\mathbf{z}$ and mutational step $\mathbf{a}$, improvement in squared distance requires $2\mathbf{z}\cdot \mathbf{a}+\Vert \mathbf{a}{\Vert }^2<0$.

An inherited sequence change that spreads to allele fixation because of a favorable effect on genotype fitness in the relevant context. The distribution of effects among substitutions differs from that among newly arising mutations.

A sequence of changes between genotypes or phenotypes under natural selection. A model with one substitution at a time is an approximation that can fail when many beneficial lineages compete.

Inherited variation already present before a focal environmental change or episode of natural selection. Reuse of an existing allele differs historically from independent origin through a new mutation.

The probability distribution of increases in genotype fitness among beneficial mutations in a specified genetic background and environment. Weighting arrival effects by fixation probability changes the distribution among successful substitutions.

A parameter measuring a relative reproductive advantage or disadvantage under a specified convention. For a haploid variant with relative genotype fitness $1+s$, positive $s$ is advantageous; other conventions require biological translation before comparison.

Competition among independently arising beneficial lineages in a biological population with little or no genetic recombination. A favorable mutation can be lost because a competing lineage spreads more successfully.

A change in linked variation accompanying the spread of a favorable allele. Its genomic signature depends on ancestry, recombination rate and whether selection acts on a new or pre-existing variant; a population bottleneck can mimic some features.

A statistic describing genetic differentiation among biological populations relative to within-population variation. High $F_{ST}$ can reflect reduced diversity within a biological population; it does not alone establish adaptive sequence divergence.

Reduced efficacy of natural selection caused by associations between selected genetic loci in finite biological populations. genetic recombination can relieve some of this interference by changing the associations.

Stochastic loss of the least mutation-loaded class in a finite biological population with little or no genetic recombination and negligible reversal of the harmful changes. Recombination can recreate some low-load combinations.

A population geneticist studies variation in allele frequencies, its evolutionary causes and the ancestry of sampled genetic material. The work combines genetics, probability and empirical data to investigate processes including natural selection, genetic drift and gene flow. For example, comparing alternative demographic models can test whether an observed pattern is better explained by biological population separation or continuing exchange, subject to the model assumptions. ^[ref]

A framework tracing sampled genetic lineages backwards to shared ancestry. A gene tree coalescence time is not generally identical to a biological population separation or migration time.

Mixing of ancestry through interbreeding between previously differentiated biological populations. A simple branching tree may not represent the resulting history.

A genome-sequencing project sampling diverse human biological populations and informing models of shared and differentiated biological population ancestry.

Stochastic changes in lineage frequency without an imposed fitness difference. In a renewing stem-cell compartment, equivalent clones can be lost or expand while the total biological population remains approximately constant.